Degradation Mechanism of All-Solid-State Li-Metal Batteries Studied by Electrochemical Impedance Spectroscopy

Eric Jianfeng Cheng; Yosuke Kushida; Takeshi Abe; Kiyoshi Kanamura

doi:10.1021/acsami.2c09841

Degradation Mechanism of All-Solid-State Li-Metal Batteries Studied by Electrochemical Impedance Spectroscopy

ACS Appl Mater Interfaces. 2022 Sep 14;14(36):40881-40889. doi: 10.1021/acsami.2c09841. Epub 2022 Aug 19.

Authors

Eric Jianfeng Cheng^{1

2}, Yosuke Kushida², Takeshi Abe¹, Kiyoshi Kanamura²

Affiliations

¹ Graduate School of Engineering, Kyoto University, Kyoto 615-8510, Japan.
² Graduate School of Urban Environmental Sciences, Tokyo Metropolitan University, Tokyo 192-0397, Japan.

Abstract

Solid-state Li-metal batteries have the potential to achieve both high safety and high energy densities. Among various solid-state fast-ion conductors, the garnet-type Li₇La₃Zr₂O₁₂ (LLZO) is one of the few that are stable to Li metal. However, the large interfacial resistance between LLZO and cathode materials severely limits the practical application of LLZO. Here a LiCoO₂ (LCO) film was deposited onto an Al-doped LLZO substrate at room temperature by aerosol deposition, and a low interfacial resistance was achieved. The LCO particles were precoated by Li₃BO₃ (LBO), which melted to join the LCO particles to the LLZO substrate at heating. All-solid-state Li/LLZO/LBO-LCO cells could deliver an initial discharge capacity of 128 mAh g^-1 at 0.2 C and 60 °C and demonstrated relatively high capacity retention of 87% after 30 cycles. The cell degradation mechanism was studied by electrochemical impedance spectroscopy (EIS) and was found to be mainly related to the increase of the interfacial resistance between LBO and LCO. In-situ SEM analysis verified the hypothesis that the increase of the interfacial resistance was caused primarily by interfacial cracking upon cycling. This study demonstrated the capability of EIS as a powerful nondestructive in-situ technique to investigate the failure mechanisms of all-solid-state batteries.

Keywords: Li7La3Zr2O12; aerosol deposition; all-solid-state Li-metal batteries; electrochemical impedance spectroscopy; in-situ scanning electron microscopy; interfacial resistance.