The mechanical properties,contact angle,thermomechanical and electrochemical properties of PE,PVDF,and ceramic separators were compared.The experimental results show that the PE separator has the largest porosity,the ...The mechanical properties,contact angle,thermomechanical and electrochemical properties of PE,PVDF,and ceramic separators were compared.The experimental results show that the PE separator has the largest porosity,the PVDF separator has the best mechanical properties,wettability,and heat resistance.Three kinds of separators were assembled into lithium-ion batteries for electrochemical tests.Among them,the PE separator has the best rate performance,and the ceramic separator has poor performance in charge-discharge cycles.At the same time,the PE and ceramic separators were tested with different amounts of electrolytes at room temperature and a high temperature,and it is found that the capacity of the PE separator is higher at room temperature,while the performance of the ceramic separator is better at a high temperature.The amount of electrolyte also has a certain influence on its electrochemical performance.展开更多
Spinel Li Mn_2O_4 microspheres and hollow microspheres with adjustable wall thickness have been prepared using controllable oxidation of Mn CO3 microspheres precursors and following solid reactions with lithium salts....Spinel Li Mn_2O_4 microspheres and hollow microspheres with adjustable wall thickness have been prepared using controllable oxidation of Mn CO3 microspheres precursors and following solid reactions with lithium salts. Scanning electron microscopy(SEM) investigations demonstrate that the microsphere morphology and hollow structure of precursors are inherited. The effect of hollow structure properties of as-prepared Li Mn_2O_4 on their performance as cathode materials for lithium-ion batteries has been studied. Electrochemical performance tests show that Li Mn_2O_4 hollow microspheres with small wall thickness exhibit both superior rate capability and better cycle performance than Li Mn_2O_4 solid microspheres and Li Mn_2O_4 hollow microspheres with thick wall. The Li Mn_2O_4 hollow microspheres with thin wall have discharge capacity of 132.7 m A·h·g-1 at C/10(14.8 m A·g-1) in the first cycle, 94.1% capacity retention at C/10 after 40 cycles and discharge capacity of 116.5 m Ah·g-1 at a high rate of 5C. The apparent lithium-ion diffusion coefficient(Dapp) of as-prepared Li Mn_2O_4 determined by capacity intermittent titration technique(CITT) varies from 10-11 to 10-8.5 cm2·s-1 showing a regular "W" shape curve plotted with test voltages. The Dapp of Li Mn_2O_4 hollow microspheres with thin wall has the largest value among all the prepared samples. Both the superior rate capability and cycle stability of Li Mn_2O_4 hollow microspheres with thin wall can be ascribed to the facile ion diffusion in the hollow structures and the robust of hollow structures during repeated cycling.展开更多
A series of manganese spinels LiMn2-yMeyO4 (Me = Li, Al, Mg) were prepared and examined by XRD and electrochemical methods. The spinels doped with Li or high content of Al can exhibit discharge capacity in the 5 V reg...A series of manganese spinels LiMn2-yMeyO4 (Me = Li, Al, Mg) were prepared and examined by XRD and electrochemical methods. The spinels doped with Li or high content of Al can exhibit discharge capacity in the 5 V region, but spinels doped with Mg do not exhibit any 5 V discharge capacity. It is also observed that the 5 V discharge capacity of Li/Al doped spinels will be greatly suppressed once calcinated at temperatures above 900 ℃ in preparation. It is suggested that the 5 V discharge capacity of Li/Al doped spinels may be originated from the special chemical/structural characteristics of spinel phases containing Li or high content of Al prepared at temperatures below 900 ℃.展开更多
基金National Natural Science Foundation of China(No.51976143)。
文摘The mechanical properties,contact angle,thermomechanical and electrochemical properties of PE,PVDF,and ceramic separators were compared.The experimental results show that the PE separator has the largest porosity,the PVDF separator has the best mechanical properties,wettability,and heat resistance.Three kinds of separators were assembled into lithium-ion batteries for electrochemical tests.Among them,the PE separator has the best rate performance,and the ceramic separator has poor performance in charge-discharge cycles.At the same time,the PE and ceramic separators were tested with different amounts of electrolytes at room temperature and a high temperature,and it is found that the capacity of the PE separator is higher at room temperature,while the performance of the ceramic separator is better at a high temperature.The amount of electrolyte also has a certain influence on its electrochemical performance.
基金Funded by the National Natural Science Foundation of China(Nos.20803056,11474226)the Fundamental Research Funds for the Central Universities(WUT:2015-IB-001,WUT:2016-IB-005)
文摘Spinel Li Mn_2O_4 microspheres and hollow microspheres with adjustable wall thickness have been prepared using controllable oxidation of Mn CO3 microspheres precursors and following solid reactions with lithium salts. Scanning electron microscopy(SEM) investigations demonstrate that the microsphere morphology and hollow structure of precursors are inherited. The effect of hollow structure properties of as-prepared Li Mn_2O_4 on their performance as cathode materials for lithium-ion batteries has been studied. Electrochemical performance tests show that Li Mn_2O_4 hollow microspheres with small wall thickness exhibit both superior rate capability and better cycle performance than Li Mn_2O_4 solid microspheres and Li Mn_2O_4 hollow microspheres with thick wall. The Li Mn_2O_4 hollow microspheres with thin wall have discharge capacity of 132.7 m A·h·g-1 at C/10(14.8 m A·g-1) in the first cycle, 94.1% capacity retention at C/10 after 40 cycles and discharge capacity of 116.5 m Ah·g-1 at a high rate of 5C. The apparent lithium-ion diffusion coefficient(Dapp) of as-prepared Li Mn_2O_4 determined by capacity intermittent titration technique(CITT) varies from 10-11 to 10-8.5 cm2·s-1 showing a regular "W" shape curve plotted with test voltages. The Dapp of Li Mn_2O_4 hollow microspheres with thin wall has the largest value among all the prepared samples. Both the superior rate capability and cycle stability of Li Mn_2O_4 hollow microspheres with thin wall can be ascribed to the facile ion diffusion in the hollow structures and the robust of hollow structures during repeated cycling.
基金Funded partly by the Fundamental Research Funds for the Central Universities (No.WHUT-2012-Ia-029)the Foundation of the Ministry of Education of China for Returned Scholars (No.2007-24)
文摘A series of manganese spinels LiMn2-yMeyO4 (Me = Li, Al, Mg) were prepared and examined by XRD and electrochemical methods. The spinels doped with Li or high content of Al can exhibit discharge capacity in the 5 V region, but spinels doped with Mg do not exhibit any 5 V discharge capacity. It is also observed that the 5 V discharge capacity of Li/Al doped spinels will be greatly suppressed once calcinated at temperatures above 900 ℃ in preparation. It is suggested that the 5 V discharge capacity of Li/Al doped spinels may be originated from the special chemical/structural characteristics of spinel phases containing Li or high content of Al prepared at temperatures below 900 ℃.
