Li2CO3 -assisted sintering of Li7La3Zr2O12 solid electrolytes for enhanced electrochemical performance

초록

In this study, Li7La3Zr2O12 (LLZO) solid electrolyte powders were synthesized, and Li2CO3 was introduced during the pelletization and sintering processes to promote grain growth. This approach aimed to reduce grain boundary fraction within the pellets and minimize interfacial resistance, thereby enhancing the structural integrity of LLZO solid electrolytes and improving the electrochemical performance of all-solid-state lithium batteries. Two systematic investigations were conducted: (1) the effect of sintering temperature (1100-1200 degrees C) on LLZO pellets processed with a fixed 10 wt% Li2CO3, and (2) the influence of varying Li2CO3 content (5-20 wt%) at the optimized sintering temperature of 1200 degrees C. XRD analysis confirmed that increasing the sintering temperature facilitated the phase transformation from tetragonal to cubic, significantly improving ionic conductivity. SEM and EDS analyses revealed that a combination of 1200 degrees C sintering and 10 wt% Li2CO3 addition yielded optimal grain growth, densification, and minimized porosity. Electrochemical measurements demonstrated that LLZO pellets sintered at 1200 degrees C with 10 wt% Li2CO3 exhibited enhanced ionic conductivity, delivering excellent discharge capacity and high initial Coulombic efficiency. Cycling tests confirmed 85% capacity retention after 50 cycles, while C-rate tests demonstrated outstanding rate capability. Overall, this study proposes a scalable and cost-effective strategy for enhancing the performance of LLZO-based solid electrolytes without the use of additional dopants, offering a promising pathway toward high-performance all-solid-state lithium batteries.

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