Correlation and the mechanism of lithium ion diffusion with the crystal structure of Li7La3Zr2O12 revealed by an internal friction technique.
Correlation and the mechanism of lithium ion diffusion with the crystal structure of Li7La3Zr2O12 revealed by an internal friction technique.
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DOI：
10.1039/c3cp55515a
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发表时间：
2014-03
期刊：
影响因子：
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通讯作者：
Xuejiang Wang;Y. Gao;Y. Xia;Z. Zhong;T. Zhang;Q. Fang
中科院分区：
文献类型：
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作者：
Xuejiang Wang;Y. Gao;Y. Xia;Z. Zhong;T. Zhang;Q. Fang
利用内耗(IF)和交流阻抗谱技术研究了锂离子与锂离子快导体Li7La3Zr2O12晶体结构的关联和输运机制。与四方相Li7La3Zr2O12的导电性差相比，Al稳定的立方相具有良好的离子导电性，室温下电导率可达1.9×10-4 S cm(-1)，这可归因于锂离子在立方相中的无序分布。在立方相中观察到明显的弛豫IF峰(标记为PC峰)，而在四方相中观察到非常弱的IF峰(标记为PT)，进一步证明了锂离子在两相中迁移的差异。Pc峰可分解为两个子峰，其活化能和驰豫时间的指前因子分别为E_1=0.41 eV和τ_01=1.2×10~(-14)S，E_2=0.35 eV和τ_2=1.9×10~(-15)S。根据立方石榴石型Li7La3Zr2O12化合物的晶体结构，提出了锂离子通过空位扩散的原子机制，即48g(96h)↔48g(96h)峰PC1和48g(96h)↔24d峰Pc2。初步认为，四方相中的弱PT峰是由于相邻的八面体晶位和空位的四面体晶位之间的跳跃过程造成的。
The correlation and transport mechanism of lithium ions with the crystal structure of a fast lithium ion conductor Li7La3Zr2O12 are mainly investigated by internal friction (IF) and AC impedance spectroscopy techniques. Compared with the poor conductivity of tetragonal Li7La3Zr2O12, the Al stabilized cubic phase exhibits a good ionic conductivity that can be up to 1.9 × 10(-4) S cm(-1) at room temperature, which can be ascribed to the disordered distribution of lithium ions in the cubic phase. A well-pronounced relaxation IF peak (labeled as peak PC) is observed in the cubic phase while a very weak IF peak (labeled as PT) is observed in the tetragonal phase, further evidencing the difference in lithium ion migration in the two phases. Peak PC can be decomposed into two sub-peaks with the activation energy and the pre-exponential factor of relaxation time being E1 = 0.41 eV and τ01 = 1.2 × 10(-14) s for the lower temperature peak PC1 and E2 = 0.35 eV and τ02 = 1.9 × 10(-15) s for the higher temperature PC2 peak, respectively. Based on the crystalline structure of a cubic garnet-type Li7La3Zr2O12 compound, an atomistic mechanism of lithium ion diffusion via vacancies is suggested, i.e. 48g(96h) ↔ 48g(96h) for peak PC1 and 48g(96h) ↔ 24d for peak PC2, respectively. The weak PT peak in the tetragonal phase is preliminarily interpreted as due to the short jump process among neighboring octahedral sites and vacant tetrahedral sites.