Synthesis of lithium garnet oxides of the compositions series Li_7-xLa₃Zr_2-xTa _xO₁₂

Abstract

In order to obtain a safe, reliable, long-lived battery system without use of flammable, volatile, and relatively unstable organic liquid-based electrolytes, lithium garnet oxides with formulas Li_7-xLa₃Zr_2-xTa _xO₁₂ (x=0.2-1) were synthesized by the solid state reaction method. Single cubic phases were observed in the composition x range between 0.2 and 1. The lattice parameters decreased with the addition of Ta due to the smaller ionic radius of Ta⁵⁺ compared with that of Zr⁴⁺, following the Vegard’s law. The total conductivity of the x = 0.3 composition is 6.03×10^-5 S·cm^-1 at room temperature with an activation energy of 0.30 eV. These lithium garnet oxides exhibit lithium ionic transport that is relevant to lithium battery application.

Keywords

solid electrolytes / cubic garnet / Ta substitution / ionic conductivity

References

[1] West AR. Ionic Conductivity of Oxides based on Li₄SiO₄[J]. Journal of Applied Electrochemistry, 1973, 3(4): 327-335.

[2] Kvist A, Lundén A. Electrical Conductivity of Solid and Molten Lithium Sulfate[J]. Zeitschrift Fur Naturforschung Teil A, 1965, 20: 235.

[3] Hong YP. Crystal Structure and Ionic Conductivity of Li₁₄Zn(GeO₄)₄ and Other New Li⁺ Superionic Conductors[J]. Materials Research Bulletin, 1978, 13(2): 117-124.

[4] Aono H, Imanaka N, Adachi G. High Li⁺ Conducting Ceramics[J]. Accounts of Chemical Research, 1994, 27(9): 265-270.

[5] Adachi G, Imnaka N, Ano H. Fast Li⁺ Conducting Ceramic Eletrolytes[J]. Advanced Materials, 1996, 8(2): 127-135.

[6] Aono H, Sugimoto E, Sadaoka Y, et al. Ionic Conductivity of the Lithium Titanium Phosphate (Li_1+XM_XTi_2−X(PO₄)₃, M = Al, Sc, Y, and La) Systems[J]. Journal of the Electrochemical Society., 1989, 136(2): 590-591.

[7] Farrington GC, Dunn BS, Briant JL. Li⁺ and Divalent Ion Conductivity in Beta and Beta″ Alumina[J]. Solid State Ionics, 1981, 3–4: 405-408.

[8] Itoh M, Inaguma Y, Jung WH, Chen LQ, et al. High Lithium Ion Conductivity in the Perovskite-type Compounds Ln_1/2Li_1/2TiO₃ (Ln=La, Pr, Nd, Sm)[J]. Solid State Ionics, 1994, 70: 203-207.

[9] Murugan R, Thangadurai V, Weppner W. Fast Lithium Ion Conduction in Garnet-Type Li₇La₃Zr₂O₁₂[J]. Angewandte Chemie International Edition, 2007, 46: 7 778-7 781.

[10] Awaka J, Kijima N, Hayakawa H, et al. Synthesis and Structure Analysis of Tetragonal Li₇La₃Zr₂O₁₂ with the Garnet-related Type Structure[J]. Journal of Solid State Chemistry, 2009, 182: 2 046-2 052.

[11] Li YT, Wang CA, Xie H, et al. High Lithium Ion Conduction in Garnet-type Li₆La₃ZrTaO₁₂[J]. Electrochemistry Communication, 2011, 13: 1 289-1 292.

[12] Logéat A, Kohler T, Eisele U, et al. From Order to Disorder: The Structure of Lithium-conducting Garnets Li_7−xLa₃Ta_xZr_2−xO₁₂ (x=0-2) [J]. Solid State Ionics, 2012, 206: 33-38.

[13] Mazza D. Remarks on a Ternary Phase in the La₂O₃-Me₂O₅-Li₂O System (Me=Nb, Ta)[J]. Materials Letters, 1988 205-207.

[14] Cussen EJ. The Structure of Lithium Garnets: Cation Disorder and Clustering in a New Family of Fast Li⁺ Conductors[J]. Chemical Communications, 2006 412-413.

[15] Shannon RD, Prewitt CT. Effective Ionic Radii in Oxides and Fluorides[J]. Acta Crystallographica Section B: Structural Crystallography and Crystal Chemistry, 1969, 25(5): 925-946.

[16] Shannon RD. Crystal Physics, Diffraction, Theoretical and General Crystallography[J]. Acta Crystallographica, 1976, 32: 751-767.

[17] Thangadurai V, Huggins RA, Weppner W. Use of Simple ac Technique to Determine the Ionic and Electronic Conductivities in Pure and Fesubstituted SrSnO₃ Perovskites[J]. Journal of Power Sources, 2002, 108: 64-69.

[18] O’Callaghan MP, Andrew SP, Jeremy JT, et al. Switching on Fast Lithium Ion Conductivity in Garnets: The Structure and Transport Properties of Li_3+xNd₃Te_2−xSb_xO₁₂[J]. Chemistry of Materials, 2008, 20(6): 2 360-2 369.