Gallium‐Doping Effects on Structure, Lithium‐Conduction, and Thermochemical Stability of Li_7‐3xGa_xLa₃Zr₂O₁₂ Garnet‐Type Electrolytes

Abstract

One of the most promising electrolytes for all‐solid‐state lithium batteries is Li7La3Zr2O12. Previously, their thermodynamic stability, Li‐ion conductivity, and structural features induced by Ga‐doping have not been empirically determined or correlated. Here, their interplay was examined for Li7−3xGaxLa3Zr2O12 with target xGa=0, 0.25, 0.50, 0.75, and 1.00 atoms per formula unit (apfu). Formation enthalpies, obtained with calorimetry and found to be exothermic at all compositions, linearly decreased in stability with increased xGa. At dilute xGa substitution, the formation enthalpy curve shifted stepwise endothermically, and the conductivity increased to a maximum, coinciding with 0.529 Ga apfu. This correlated with percolation threshold analysis (0.558 Ga apfu). Further substitution (0.787 Ga apfu) produced a large decrease in the stability and conductivity due to a large increase in point defects and blocked Li‐migration pathways. At xGa=1.140 apfu, a small exothermic shift was related to defect cluster organization extending the Li hopping distance and decreased Li‐ion conductivity.

Dopant-induced modulation of lithium-ion conductivity in cubic garnet solid electrolytes: a first-principles study

“…The dopant content in this study is controlled at 0.125, resulting in the doped LLZO formula of Li 6.625 A 0.125 La 3 Zr 16 O 12 (A = Ga, Al, and Fe). As supported by previous experimental studies, 22–25 c-LLZO doped with Ga, Al, or Fe maintains a consistent and stable cubic phase with such diluted dopant content. We employed first-principles density functional theory (DFT) calculations to identify the most energetically favorable configurations in accordance with the Li distribution principle to minimize the repulsion force 26 and considered two possible doping scenarios: replacing an existing Li atom or occupying an empty tetrahedral (24d) site.…”

Electrochemical and Mechanical Performance According to Regulating Sintering Time of Cubic Li6.1Ga0.3La3Zr2O12 Solid Electrolyte

“…The shapes of the XRD patterns for all the samples are identical with no significant secondary peaks. The diffraction peaks of both samples appearing at 17°, 20°, 25°, 27°, 30°, 32°, 34°, 36°, 37°, 43°, 44°, 47°, and 49° could be assigned to (211), (220), (321), (400), (420), (332), (422), (431), (521), (532), (620), (631), and (444) peaks, respectively . Especially, the strong (321), (420), and (422) peaks of both samples indicate a well-synthesized cubic garnet-type phase. ,, However, the full-width at half-maximum (fwhm) value of the (420) peak (Figure b) for LGLZO sintered for 10 h (0.075°) is narrower compared to that of LGLZO sintered for 20 h (0.094°), indicating better crystallinity of LGLZO sintered for 10 h. Figure c shows the Rietveld refinement result for both samples.…”

Reinforcing ionic conductivity and alleviating dendrite propagation of dense cubic Ga0.3Li6.1La3Zr2O12via two-step sintering

“…It can be seen that the majority of Ga is widely and uniformly distributed, which conrms the substitution of Li ions with Ga in the garnet type structure. 24 The XRD patterns of the as-prepared Ga-LLZO samples under different sintering conditions are exhibited in Fig. 2.…”

“…It can be seen that the majority of Ga is widely and uniformly distributed, which confirms the substitution of Li ions with Ga in the garnet type structure. 24…”