Advanced Electrochemical Analysis of All-Solid-State Battery Electrodes Using Novel Potential-Controllable Symmetric Cell

• Published in: Electrochimica acta 2023-11, Vol.468, p.143154, Article 143154
• Main Authors: Min, Yu-Jeong, Lee, Ga-Eun, Seong, Ju Yeong, Shin, Heon-Cheol
• Format: Article
• Language: English
• Subjects: All-solid-state battery; Diffusion coefficient; Electrochemical analysis; Interface; Symmetric cell
• ISSN: 0013-4686
• DOI: 10.1016/j.electacta.2023.143154

In this study, we propose a novel potential-controllable symmetric cell (PCSC) for the reliable analysis of the electrode/electrolyte interface and bulk characteristics of the active material in an all-solid-state battery (ASSB). Unlike a conventional symmetric cell, which requires the disassembly and reassembly of two unit cells with the same voltage to analyze the reactions at specific potentials, our PCSC self-adjusts the potential by lithiating/delithiating the electrodes without requiring dismantling. Specifically, a mesh-like temporary counter electrode was inserted into the center of the solid electrolyte inside the cell to allow voltage regulation of both electrodes without interfering with ion transport through the electrolyte. This is particularly useful for interpreting the reactions in ASSB, which are practically impossible to reassemble after dismantling. In addition, it eliminates the impedance measurement errors associated with the distortion of the internal structure induced by the reference electrode in a three-electrode cell, which is more detrimental to an ASSB than a conventional liquid electrolyte-based battery. As a practical example, we comparatively analyzed the characteristics of a LiNbO3-coated LiNi0.8Co0.1Mn0.1O3 (c-NCM811) cathode using conventional test cells (two- or three-electrode all-solid-state half cells) and an all-solid-state PCSC. The PCSC exhibited a clearer interfacial signal for c-NCM811 than that obtained from a conventional two-electrode half-cell. Furthermore, compared to the three-electrode all-solid-state half-cell, the PCSC provided a relatively well-resolved interfacial reaction signal. The bulk properties of c-NCM811 proved that our PCSC provided very reliable and consistent Li diffusion coefficients using various methods, including the constant phase element-restricted diffusion model, galvanostatic intermittent titration technique, and the Warburg–blocking transition-frequency estimation method.