Controlling Dendrite Formation for Long-Term Cyclability and Fast Li<SUP>+</SUP> Diffusion Kinetics in Solid-State Electrolyte Li7La3Zr2O12

초록

Ga-doped Li7La3Zr2O12 (Ga-LLZO) solid-state electrolyte is a promising materialfor advancedbatteries due to its superior ionic conductivity and mechanical properties.However, Ga-LLZO is challenged by high grain boundary (GB) resistanceand dendrite propagation. Therefore, in this study, we suggest thetwo-step sintering (TSS) method for controlling the microstructure,resulting in lower GB resistance and achieving superior dendrite resistance.To elucidate the cycling performance, a critical current density (CCD)test was performed on a Ga-LLZO sample fabricated with TSS. As a result,the Ga-LLZO sample fabricated with TSS demonstrates a superior CCDvalue of 0.32 mA cm(-2) as well as shows stable cyclingat a current density of 0.2 mA cm(-2). According tothe impedance analysis, the sample fabricated with TSS demonstratesa significant increase in ionic conductivity compared to the samplefabricated with the conventional sintering (CS) method. This phenomenonimplies that the enhanced sintering technique of TSS can reduce theGB resistance and dendrite formation by achieving the densificationand tight GB. Extensive investigation into the dendrite formationmechanism has provided compelling evidence that dendrites are notsolely composed of pure Li but rather consist of a compound containingboth C and O elements. This finding significantly contributes to theunderstanding of the composition and nature of dendrites in Ga-LLZO,shedding light on their role in the acceleration of the phase decompositionprocess.

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