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Structural and Electrochemical Consequences of Al and Ga Cosubstitution in Li7La3Zr2O12 Solid Electrolytes.

Rettenwander D, Redhammer G, Preishuber-Pflügl F, Cheng L, Miara L, Wagner R, Welzl A, Suard E, Doeff MM, Wilkening M, Fleig J, Amthauer G - Chem Mater (2016)

Bottom Line: The phase transition was located at an Al:Ga substitution ratio of 0.05:0.15 and is accompanied by a significant lowering of the activation energy for Li-ion transport to 0.26 eV.The increase in Ga content is also associated with better densification and smaller grains and is accompanied by a change in the area specific resistance (ASR) from 78 to 24 Ω cm(2), the lowest reported value for LLZO so far.These results illustrate that understanding the structure-properties relationships in this class of materials allows practical obstacles to its utilization to be readily overcome.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry and Physics of Materials, University of Salzburg , 5020, Salzburg, Austria.

ABSTRACT

Several "Beyond Li-Ion Battery" concepts such as all solid-state batteries and hybrid liquid/solid systems envision the use of a solid electrolyte to protect Li-metal anodes. These configurations are very attractive due to the possibility of exceptionally high energy densities and high (dis)charge rates, but they are far from being realized practically due to a number of issues including high interfacial resistance and difficulties associated with fabrication. One of the most promising solid electrolyte systems for these applications is Al or Ga stabilized Li7La3Zr2O12 (LLZO) based on high ionic conductivities and apparent stability against reduction by Li metal. Nevertheless, the fabrication of dense LLZO membranes with high ionic conductivity and low interfacial resistances remains challenging; it definitely requires a better understanding of the structural and electrochemical properties. In this study, the phase transition from garnet (Ia3̅d, No. 230) to "non-garnet" (I4̅3d, No. 220) space group as a function of composition and the different sintering behavior of Ga and Al stabilized LLZO are identified as important factors in determining the electrochemical properties. The phase transition was located at an Al:Ga substitution ratio of 0.05:0.15 and is accompanied by a significant lowering of the activation energy for Li-ion transport to 0.26 eV. The phase transition combined with microstructural changes concomitant with an increase of the Ga/Al ratio continuously improves the Li-ion conductivity from 2.6 × 10(-4) S cm(-1) to 1.2 × 10(-3) S cm(-1), which is close to the calculated maximum for garnet-type materials. The increase in Ga content is also associated with better densification and smaller grains and is accompanied by a change in the area specific resistance (ASR) from 78 to 24 Ω cm(2), the lowest reported value for LLZO so far. These results illustrate that understanding the structure-properties relationships in this class of materials allows practical obstacles to its utilization to be readily overcome.

No MeSH data available.


Related in: MedlinePlus

Lattice parameter (a0) (a) and Li sitedistribution (b) in Li6.4Al0.2–xGaxLa3Zr2O12, with x = 0.00, 0.05, 0.10, 0.15,and 0.20.
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fig3: Lattice parameter (a0) (a) and Li sitedistribution (b) in Li6.4Al0.2–xGaxLa3Zr2O12, with x = 0.00, 0.05, 0.10, 0.15,and 0.20.

Mentions: Polycrystalline samples of LLZO:Al0.20–xGax with x = 0.00–0.20were obtained from the pellets and used for the structure determination(XRD, SC-XRD, NPD). Analysis of systematic extinctions of Bragg peaksin the single crystal data sets of the Al-rich compositions unambiguouslyyield the common garnet space group Ia3̅d for LLZO:Al0.20Ga0.00, LLZO:Al0.15Ga0.05, and LLZO:Al0.10Ga0.10. For compositions LLZO:Al0.05Ga0.15 and LLZO:Al0.00Ga0.20, the acentric space group I4̅3d was observed as described in detail byWagner et al. (2016), recently.18 Basicstructural data are compiled in Table 1. The Li-ion distribution as well as the lattice parameteras a function of the proportion of Ga is illustrated in Figure 3.


Structural and Electrochemical Consequences of Al and Ga Cosubstitution in Li7La3Zr2O12 Solid Electrolytes.

Rettenwander D, Redhammer G, Preishuber-Pflügl F, Cheng L, Miara L, Wagner R, Welzl A, Suard E, Doeff MM, Wilkening M, Fleig J, Amthauer G - Chem Mater (2016)

Lattice parameter (a0) (a) and Li sitedistribution (b) in Li6.4Al0.2–xGaxLa3Zr2O12, with x = 0.00, 0.05, 0.10, 0.15,and 0.20.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4836877&req=5

fig3: Lattice parameter (a0) (a) and Li sitedistribution (b) in Li6.4Al0.2–xGaxLa3Zr2O12, with x = 0.00, 0.05, 0.10, 0.15,and 0.20.
Mentions: Polycrystalline samples of LLZO:Al0.20–xGax with x = 0.00–0.20were obtained from the pellets and used for the structure determination(XRD, SC-XRD, NPD). Analysis of systematic extinctions of Bragg peaksin the single crystal data sets of the Al-rich compositions unambiguouslyyield the common garnet space group Ia3̅d for LLZO:Al0.20Ga0.00, LLZO:Al0.15Ga0.05, and LLZO:Al0.10Ga0.10. For compositions LLZO:Al0.05Ga0.15 and LLZO:Al0.00Ga0.20, the acentric space group I4̅3d was observed as described in detail byWagner et al. (2016), recently.18 Basicstructural data are compiled in Table 1. The Li-ion distribution as well as the lattice parameteras a function of the proportion of Ga is illustrated in Figure 3.

Bottom Line: The phase transition was located at an Al:Ga substitution ratio of 0.05:0.15 and is accompanied by a significant lowering of the activation energy for Li-ion transport to 0.26 eV.The increase in Ga content is also associated with better densification and smaller grains and is accompanied by a change in the area specific resistance (ASR) from 78 to 24 Ω cm(2), the lowest reported value for LLZO so far.These results illustrate that understanding the structure-properties relationships in this class of materials allows practical obstacles to its utilization to be readily overcome.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry and Physics of Materials, University of Salzburg , 5020, Salzburg, Austria.

ABSTRACT

Several "Beyond Li-Ion Battery" concepts such as all solid-state batteries and hybrid liquid/solid systems envision the use of a solid electrolyte to protect Li-metal anodes. These configurations are very attractive due to the possibility of exceptionally high energy densities and high (dis)charge rates, but they are far from being realized practically due to a number of issues including high interfacial resistance and difficulties associated with fabrication. One of the most promising solid electrolyte systems for these applications is Al or Ga stabilized Li7La3Zr2O12 (LLZO) based on high ionic conductivities and apparent stability against reduction by Li metal. Nevertheless, the fabrication of dense LLZO membranes with high ionic conductivity and low interfacial resistances remains challenging; it definitely requires a better understanding of the structural and electrochemical properties. In this study, the phase transition from garnet (Ia3̅d, No. 230) to "non-garnet" (I4̅3d, No. 220) space group as a function of composition and the different sintering behavior of Ga and Al stabilized LLZO are identified as important factors in determining the electrochemical properties. The phase transition was located at an Al:Ga substitution ratio of 0.05:0.15 and is accompanied by a significant lowering of the activation energy for Li-ion transport to 0.26 eV. The phase transition combined with microstructural changes concomitant with an increase of the Ga/Al ratio continuously improves the Li-ion conductivity from 2.6 × 10(-4) S cm(-1) to 1.2 × 10(-3) S cm(-1), which is close to the calculated maximum for garnet-type materials. The increase in Ga content is also associated with better densification and smaller grains and is accompanied by a change in the area specific resistance (ASR) from 78 to 24 Ω cm(2), the lowest reported value for LLZO so far. These results illustrate that understanding the structure-properties relationships in this class of materials allows practical obstacles to its utilization to be readily overcome.

No MeSH data available.


Related in: MedlinePlus