研究锂空气电池石墨烯正极介观传质的机理,采用Materials-studio软件构建包含石墨烯、H2O、OH-、Li+和O2的介观模型,并应用粗粒化分子动力学的方法对体系中各珠子的传质特性进行介观分析,研究温度、石墨烯层数、石墨烯种类和石墨烯浓度对H2O、OH-、Li+和O2各珠子扩散系数的影响,以及对Li+-OH-、H2O-O2各珠子径向分布函数的影响。结果表明,随着体系内温度的升高,H2O、OH-、Li+和O2的扩散系数增大,Li+-OH-、H2O-O2径向分布函数峰值降低,分布的有序性降低;随着石墨烯层数的增加,H2O、OH-、Li+和O2的扩散系数减小,Li+-OH-、H2O-O2径向分布函数的峰值不变;随着不同层数石墨烯种类和浓度的增加,H2O、OH-、Li+和O2的扩散系数减小。因此,控制体系温度,减少石墨烯的层数,有利于体系中各珠子扩散系数的提升,提升锂空气电池的整体性能。
The mechanism of positive electrode mesoscopic mass transfer of graphene in lithium-air battery was studied.Materials-studio software was used to construct mesoscopic models including graphene,H2O,OH-,Li+ and O2,and the mesoscopic analysis of mass transfer characteristics of each bead in the system was carried out by means of coarse-grained molecular dynamics,the effects of temperature,number of graphene layers,types of graphene and graphene concentration on the diffusion coefficients of each bead of H2O,OH-,Li+ and O2,as well as the radial distribution functions of each bead of Li+-OH- and H2O-O2 were studied.The results shown that with the increase of temperature in the system,the diffusion coefficients of H2O,OH-,Li+ and O2 increased,the radial distribution function peak value of Li+-OH- and H2O-O2 decreased,and the distribution order decreased.As the number of graphene layers increased,the diffusion coefficients of H2O,OH-,Li+ and O2 decreased,and the peak values of the radial distribution functions of Li+-OH- and H2O-O2 remained unchanged.The diffusion coefficients of H2O,OH-,Li+ and O2 decreased with the increase of different graphene types and concentrations.Therefore,controlling the temperature of the system and reducing the number of graphene layers were conducive to the improvement of the diffusion coefficient of each bead in the system and the overall performance of the lithium-air battery.
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