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Deep hydration of an Li_7-3xLa₃Zr₂M^III_xO₁₂ solid-state electrolyte material: a case study on Al- and Ga-stabilized LLZO.

ABSTRACT: Single crystals of an Li-stuffed, Al- and Ga-stabilized garnet-type solid-state electrolyte material, Li₇La₃Zr₂O₁₂ (LLZO), have been analysed using single-crystal X-ray diffraction to determine the pristine structural state immediately after synthesis via ceramic sintering techniques. Hydrothermal treatment at 150 °C for 28 d induces a phase transition in the Al-stabilized compound from the commonly observed cubic Ia-3d structure to the acentric I-43d subtype. Li^I ions at the interstitial octahedrally (4 + 2-fold) coordinated 48e site are most easily extracted and Al^III ions order onto the tetrahedral 12a site. Deep hydration induces a distinct depletion of Li^I at this site, while the second tetrahedral site, 12b, suffers only minor Li^I loss. Charge balance is maintained by the incorporation of H^I, which is bonded to an O atom. Hydration of Ga-stabilized LLZO induces similar effects, with complete depletion of Li^I at the 48e site. The Li^I/H^I exchange not only leads to a distinct increase in the unit-cell size, but also alters some bonding topology, which is discussed here.

SUBMITTER: Redhammer GJ

PROVIDER: S-EPMC8725724 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description: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 cm2, 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.

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Deep hydration of an Li_7-3xLa₃Zr₂M^III_xO₁₂ solid-state electrolyte material: a case study on Al- and Ga-stabilized LLZO.

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Deep hydration of an Li7-3xLa3Zr2MIIIxO12 solid-state electrolyte material: a case study on Al- and Ga-stabilized LLZO.

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OmicsDI is part of the ELIXIR infrastructure

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Deep hydration of an Li_7-3xLa₃Zr₂M^III_xO₁₂ solid-state electrolyte material: a case study on Al- and Ga-stabilized LLZO.