Low temperature synthesis of garnet solid state electrolytes: Implications on aluminium incorporation in Li7La3Zr2O12

Abstract

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Water based synthesis of highly conductive GaxLi7−3xLa3Hf2O12 garnets with comparable critical current density to analogous GaxLi7−3xLa3Zr2O12 systems

“…Ga-LLHO systems demonstrate high total ionic conductivity of 0.382 mS cm -1 at 28°C, and 1.04 mS cm -1 at 63°C, which represents an impressive value, especially since the pellet only achieved 87% relative density. The conductivity values are in line with many cubic LLZO (and other garnet) phases and are similar to Ga-LLZO values with higher relative densities 55,56,58,59,[62][63][64][65] . These values therefore represent notably higher conductivities for a doped LLHO garnet compared to the Al, Ta doped samples reported in the literature, while the fact that it has also been synthesised at considerably lower temperature is also significant 46,51,53 .…”

“…Al-LLHO has overlapping semicircles indicating combined bulk and grain boundary contributions. Nyquist plots for t-LLHO and Al-LLHO were fit to two R/CPE parallel components in connected in series, illustrative of bulk and grain boundary resistance, and are similar to those plots for LLZO systems elsewhere 23,42,43,[55][56][57][58][59][60] 51 and Baklanova et al 46 respectively, however the Al-LLHO synthesis reported by the latter group required three heating cycles (900-1200°C) and over 40 hours to form the material.…”

X-ray pair distribution function analysis and electrical and electrochemical properties of cerium doped Li5La3Nb2O12 garnet solid-state electrolyte

“…[12][13][14] The highly conductive cubic phase can be stabilised through the creation of lithium vacancies, and the optimum conductivity is found for lithium contents of 6.4-6.6 per garnet formula unit. [15][16][17][18][19][20][21][22][23][24][25] In addition, to facilitate the practical application of ASSBs, issues such as high interfacial resistances between the electrode and electrolyte, and the lithium dendrite penetration problem within solid state electrolytes have attracted much attention in recent years. [26][27][28][29] The interfacial impedance between the garnet and electrode mainly arises from the poor contact in association with microscopic voids and grain boundaries of garnet, as well as an insulating Li 2 CO 3 surface layer formed in air initiated by the proton/lithium exchange at the surface.…”

Evaluation of the effect of site substitution of Pr doping in the lithium garnet system Li5La3Nb2O12

“…16,29,30 Consequently, the majority of c-LLZO doping strategies lead to conductivities ∼10 −4 S cm −1 , or lower, and are suboptimal compared with current LIB liquid electrolytes. [31][32][33][34][35][36][37][38] Therefore, it is of interest to investigate alternative doping strategies of other lithium garnet systems, such as Li 5 La 3 Nb 2 O 12 (LLNO). This system was the first to show fast Li-ion conductivity, and outside of detailed examinations of the lithium migration pathways, has now been superseded by research on c-LLZO.…”