第一性原理对氮掺杂石墨烯作为锂-空电池阴极材料还原氧分子的机理研究  

First-principles study of reduction mechanism of oxygen molecule using nitrogen doped graphene as cathode material for lithium air batteries

作　　者：侯滨朋 淦作亮 雷雪玲 钟淑英 徐波 欧阳楚英[1] Hou Bin-Peng;Gan Zuo-Liang;Lei Xue-Ling;Zhong Shu-Ying;Xu Bo;Ouyang Chu-Ying(Laboratory of Computational Materials Physics,Department of Physics,Jiangxi Normal University,Nanchang 330022,China)

机构地区：[1]江西师范大学物理系计算材料物理实验室

出　　处：《物理学报》2019年第12期297-310,共14页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:11764019,11564016,11664012)资助的课题~~

摘　　要：采用第一性原理,研究了不同浓度的氮掺杂石墨烯还原氧分子的机理.结果表明,掺杂氮原子以后,氧分子的吸附能增大,获得的电荷增多,O-O键长变长,说明氮掺杂石墨烯增强了对氧分子的还原能力.进一步分析发现,氧分子吸附之后,氮原子和氧分子均从碳原子上获得电荷,氮原子同时也向氧分子转移电荷,从而使氧分子与基底的相互作用增强.另外,通过对比不同浓度的氮原子掺杂,发现3.13 at%的氮原子掺杂比例对氧分子的还原性能最好.Lithium-oxygen battery possesses an extremely high theoretical energy density(≈ 3500 W·h·kg-1), and is an ideal next-generation energy storage system. The ideal operation of lithium-oxygen batteries is based on the electrochemical formation(discharge) and decomposition(charge) of lithium peroxide(Li2 O2). At the beginning of the discharge, oxygen is reduced on the electrode, forming an oxygen radical(O2-). The O2-successively combines with an Li ion, forming the metastable LiO2. The LiO2 may subsequently undergo two different reaction pathways: a chemical disproportionation and a continuous electrochemical reduction, thereby resulting in the formation of Li2 O2. Therefore, the oxygen reduction reaction(ORR) is an important step in the discharge process. Studies have shown that graphene is considered as the most promising cathode material for non-aqueous lithium-oxygen batteries. Moreover, it is found that nitrogen-doped graphene has higher electrocatalytic activity than intrinsic graphene for the ORR. However, up to now, the mechanism of improving the ORR for nitrogen-doped graphene is still unclear, and the effects of different N-doping concentrations on the ORR have not been reported. In this work, on the basis of the first-principles calculations, the reduction mechanism of O2 molecule by nitrogen-doped graphene with different N concentrations is studied. Results show that after doping N atoms, the adsorption energy of O2 molecules increases, the O-O bond length is elongated,and the transferred charge increases, which indicates that nitrogen-doped graphene enhances the reduction ability of O2 molecule. Bader charge analysis shows that both N atom and O2 molecule obtain charges from C atom, and N atom also provides charges for O2 molecule, which is consistent with the electronegativity of carbon, nitrogen and oxygen. This charge transfer results in the stronger interaction between the O2 molecule and the substrate, and can reveal the reason why nitrogen-doped graphene can improve the ORR. In addition,it is

关 键 词：锂-空电池 氮掺杂石墨烯 氧分子吸附 氧还原机理 第一性原理 

分 类 号：TM911.41[电气工程—电力电子与电力传动]