Mechanism of Ion Conduction and Dynamics in Tris( N , N -dimethylformamide) Perchloratosodium Solid Electrolytes
Mechanism of Ion Conduction and Dynamics in Tris( N , N -dimethylformamide) Perchloratosodium Solid Electrolytes
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三(N,N-二甲基甲酰胺)高氯酸钠固体电解质中的离子传导和动力学机制
DOI：
10.1021/acs.jpcc.1c09005
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发表时间：
2022
期刊：
影响因子：
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通讯作者：
Venkatnathan, Arun
中科院分区：
文献类型：
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作者：
Prakash, Prabhat;Shylendran, Ardhra;Fall, Birane;Zdilla, Michael J.;Wunder, Stephanie L.;Venkatnathan, Arun
（DMF） 3naclo4是一种软固体共晶电解质，具有Na+离子通道，可以通过施加压力或加热可逆地转化为导电性较低的形式（DMF） 2naclo4，从而形成可熔化或可压铸的电解质。在3:1的化学计量中进行的分子动力学模拟表明，Na+离子通过一维通道传导，这得到了van-Hove自相关函数分析的支持。模拟结果表明，常温下Na+离子的迁移数为0.43，高温下Na+离子的迁移数超过0.5。MD模拟计算出Na+离子扩散的活化能为45 kJ mol-1。利用周期密度功能理论计算评估了3:1晶体中Na+离子迁移的最小能量路径，该路径为Na+离子的传导提供了33 kJ mol-1的势垒，与25 kJ mol-1的实验值基本一致。Na+离子在传导过程中的运动是由空位驱动的，因为空位位置的存在使Na+离子能够发生跳跃事件。激活能是钠离子通过过渡态离开八面体配位DMF配体场的惩罚，在过渡态中，只有三个DMF分子形成3-O-Na三角形平面几何结构，而没有clo4参与过渡态的配位球。相比之下，2:1化学计量的计算活化能势垒更高（Ea，DFT= 43 kJ mol-1,Ea,exp= 49 kJ mol-1），至少部分原因是高氯酸盐阴离子与Na+离子在过渡态的部分配位。
(DMF)3NaClO4is a soft-solid cocrystalline electrolyte with channels of Na+ions, which can be reversibly converted to a less conductive form (DMF)2NaClO4by the application of pressure or heat, leading to a melt- or press-castable electrolyte. Molecular dynamics simulations performed on the 3:1 stoichiometry suggest that Na+ions conduct via a one-dimensional channel, which is supported by van-Hove autocorrelation function analysis. The simulations show that the transference number for Na+ions is 0.43 at room temperature and exceeds 0.5 at higher temperatures in the molten mixture. The calculated activation energy for the diffusion of Na+ions from MD simulations is 45 kJ mol–1. The minimum-energy path of Na+ion migration in a 3:1 crystal is assessed using periodic density functional theory calculations, which provides a barrier of 33 kJ mol–1for Na+ion conduction, in reasonable agreement with the experimental value of 25 kJ mol–1. The motion of Na+ions during conduction is vacancy-driven because the presence of a vacancy site enables jump events for Na+ions. The activation energy is the penalty for a sodium ion to leave the octahedrally coordinated DMF ligand field via a transition state where only three molecules of DMF form a 3-O-Na trigonal planar geometry, with no involvement of ClO4–in the coordination sphere of the transition state. In contrast, the calculated activation energy barrier for the 2:1 stoichiometry is higher (Ea,DFT= 43 kJ mol–1,Ea,exp= 49 kJ mol–1) due at least in part to the partial coordination of strongly binding perchlorate anions with Na+ions in the transition state.