Enhancing Fast Lithium Ion Conduction in Li4GeO4–Li3PO4 Solid Electrolytes

作者：Guowei Zhao, Kota Suzuki, Masao Yonemura, Masaaki Hirayama, Ryoji Kanno · 发表于：ACS Applied Energy Materials · 年份：2019 · DOI：10.1021/acsaem.9b01152 · 被引用次数：49 · 研究领域：Advancements in Battery Materials、Advanced Battery Materials and Technologies、Thermal Expansion and Ionic Conductivity

Codoping the lithium superionic conductor (LISICON) Li 3.75 Ge 0.75 P 0.25 O 4 system with various aliovalent cations M (M = Mg 2+, B 3+, Al 3+, Ga 3+, and V 5+ ) was conducted via a solid-state reaction method following the chemical formula Li 3.75 ± y (Ge 0.75 P 0.25 ) 1– x M x O 4 to obtain high-conductivity lithium ionic conductors. The highest ionic conductivity (5.1 × 10 –5 S cm –1 ) was obtained at 25 °C for Li 3.53 (Ge 0.75 P 0.25 ) 0.7 V 0.3 O 4, which also exhibited low activation energy of 0.43(2) eV. Rietveld refinement using neutron diffraction data revealed that the Ge 4+, P 5+, and V 5+ cations occupied the same crystallographic site, and their ratios were consistent with the nominal ratios of Li 3.53(6) Ge 0.5264(17) P 0.1743(12) V 0.2993(7) O 4 . Compared with the framework of γ-Li 3 PO 4, which has only two fully occupied crystallographically different tetrahedral site lithium ions (Li: 8d, Li2: 4c), two additional partially occupied crystallographic octahedral lithium ion sites that dominantly contribute to lithium conduction were detected. The codoping strategy contributed to the compositional and structural optimization of the LISICON system, affording enhanced ion-conducting properties.