Joon-ho Choi

POSTECH / Solid-State Battery Electrochemistry

Advisor: Prof. Byung-Kuk Yoo

Joon-ho Choi optimises the sintering conditions for garnet-structured Li₇La₃Zr₂O₁₂ (LLZO) solid electrolyte pellets to achieve the combination of high ionic conductivity (>1 mS/cm at room temperature) and mechanical hardness (>5 GPa) required to suppress lithium dendrite penetration in all-solid-state batteries at aggressive current densities. At POSTECH's Department of Materials Science and Engineering, supervised by Prof. Byung-Kuk Yoo, he employs spark plasma sintering with a computer-controlled pressure–temperature trajectory to avoid the 150 °C-wide window where Li₂ZrO₃ impurity formation reduces conductivity while simultaneously preventing lithium volatilisation that creates interfacial voids. His impedance spectroscopy analysis of 340 sintered pellets across the SPS parameter space has identified a 2-minute dwell at 1,150 °C under 50 MPa as the global optimum, achieving 1.4 mS/cm ionic conductivity with Vickers hardness of 6.1 GPa. In situ XRD measurements during galvanostatic cycling confirm that dendrite initiation at Li/LLZO interfaces follows grain boundary oxidation kinetics that he has modelled analytically. A research collaboration with Samsung SDI's all-solid-state battery programme funds his in situ characterisation infrastructure and provides industrial validation of his LLZO optimisation protocol.