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2 Materials Science Poland

2 2020

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Facile preparation of Co@Co3O4@Nitrogen doped carbon composite from ionic liquid as anode material for high performance lithium-ion batteries

100%

Xiao M. , Meng Y. , Duan C. , Zhu F. , Zhang Y.

tom Vol. 38, No. 4

601--612

Co@Co3O4@Nitrogen doped carbon (Co@Co3O4@NDC) composite is synthesized by high temperature carbonization of ionic liquids followed by low temperature thermal oxidation. In the process of high temperature carbonization, cobalt ions are reduced to metallic cobalt, producing Co@Nitrogen doped carbon (Co@NDC). Co@Co3O4 @NDC composite is obtained after low temperature oxidation, in which a part of the metallic cobalt is oxidized to Co3O4. The structural characterizations indicate that the composite is composed of three crystalline phases (carbon, Co and Co3O4). The results of transmission electron microscopy study show that the carbon materials not only coat the Co@Co3O4 nanoparticles, but also form carbon network that connects the Co@Co3O4 nanoparticles. This conductive carbon network is beneficial to improve the electrochemical performance of the composite. The electrochemical test results show that the Co@Co3O4 @NDC composite exhibits excellent electrochemical performance, delivering the discharge capacities of 790 and 304 mAh∙g-1 after 1500 cycles at 5 C and 10 C. This excellent electrochemical performance is due to synergistic effects of Co3O4, cobalt nanoparticles embedded in carbon which has high conductivity, and nitrogen functional groups.

Influence of nitrogen configuration on the electrochemical properties of carbonized poly(acrylonitrile)-ionic liquid as anode materials in lithium ion batteries

86%

Wang L. , Meng Y. , Du M. , Wang G. , Xia J. , Zhu F. , Zhang Y.

tom Vol. 38, No. 4

518--525

A sequence of N-doped carbon materials has been synthesized using poly(acrylonitrile)-ionic liquid copolymers as carbon precursors. The nitrogen content and configuration in carbon materials has been changed regularly within a certain range by adjusting the proportion of ionic liquids. We found that the capacity and rate performance increased dramatically after the introduction of ionic liquids, which was attributed to incorporation of higher amount pyridinic-N, pyrrolic-N into the carbon materials. Besides, with the increase of the graphitic-N, the initial Coulombic efficiency decreased from 58.5 % to 53.47 % and the RSEI raised from 66.34 W to 140.96 W, which was attributed to the higher cohesive energy of Li dimmer than adsorption energy of graphitic-N with Li, since more lithium clusters during the formation of SEI film were formed. The electrochemical tests also revealed the negative role of graphitic-N in the capacity. Therefore, this work provides a feasible method to design the nitrogen content and configuration of the N-doped carbon materials.