Improving Contact Impedance via Electrochemical Pulses Applied to Lithium–Solid Electrolyte Interface in Solid-State Batteries

Stabilizing interfaces in solid-state batteries (SSBs) is crucial for development of high energy density batteries. In this work, we report a facile electrochemical protocol to improve the interfacial impedance and contact at the interface of Li | Li_6.25Al_0.25La₃Zr₂O₁₂ (LALZO). Application of short duration, high-voltage pulses to poorly formed interfaces leads to lower contact impedance. It is found that the local high current density that results from these pulses at the vicinity of the interfacial pores can lead to a better contact between Li and LALZO because of local Joule heating, as supported by theoretical simulations. The pulse technique, which has also been applied to a Li | Li_6.4La₃Zr_1.4Ta_0.6O₁₂ (LLZTO) | LiNi_0.6Mn_0.2Co_0.2O₂ (NMC622) cell, results in remarkable reduction of the charge-transfer resistance. Ex situ characterizations, which include X-ray photoelectron spectroscopy and scanning electron microscopy techniques, reveal that there is no detrimental effects of the pulse on cathode and solid electrolyte bulks and interfaces. This electrochemical pulse technique sheds light on a facile, nondestructive method that has the potential to significantly improve the interfacial contacts in a solid-state battery configuration.