Journal
CHEMSUSCHEM
Volume 14, Issue 12, Pages 2621-2630Publisher
WILEY-V C H VERLAG GMBH
DOI: 10.1002/cssc.202100526
Keywords
batteries; calorimetry; electrolytes; gallium doping; thermochemistry
Funding
- Center for Hierarchical Waste Form Materials, an Energy Frontier Research Center - U.S. Department of Energy, Office of Science, Basic Energy Sciences [DE-SC0016574]
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The study examined the interplay of Li7-3xGaxLa3Zr2O12 electrolytes with various levels of Ga-doping, finding that stability and conductivity decrease with increased Ga substitution due to an increase in defects and blocked ion migration pathways. Excessive Ga doping beyond a certain threshold led to a significant decrease in stability and conductivity by disrupting the Li-ion hopping distance.
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.
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