Degradation mechanism of all‐solid‐state lithium‐ion batteries with argyrodite Li_7−xPS_6−xCl_x sulfide through high‐temperature cycling test

Abstract

Sulfide‐based all‐solid‐state lithium‐ion batteries (LIBs) are promising replacements for conventional liquid electrolyte LIBs. However, their degradation mechanisms and analysis methods are poorly understood. Herein, the degradation mechanism of an argyrodite‐type sulfide‐based all‐solid‐state prototype LIB cell is reported. Furthermore, an analysis method for all‐solid‐state batteries using charge/discharge cycle tests at 100°C followed by the disassembly analysis of cells before and after accelerated degradation tests is reported. Based on the findings of this study, the degradation of the prototype cell is classified as follows: (i) solid electrolyte (SE) oxidation in the positive electrode, which recovers battery capacity and increases resistance; (ii) SE reduction in the negative electrode, which decreases capacity; (iii) lithium deposition on/in the negative electrode, which decreases capacity; and (iv) capacity loss of the positive electrode, which decreases capacity. These degradation reactions appear to occur simultaneously. These findings are expected to aid the development of sulfide‐based solid‐electrolyte LIBs with improved safety and energy densities.

Thermal, Electrical, and Environmental Safeties of Sulfide Electrolyte-Based All-Solid-State Li-Ion Batteries

“…A sudden voltage drop can be the signature of the direct electrical shorting of a battery. As high temperatures accelerate chemical degradation, the marginal voltage drop is also expected in ASLIBs . As shown in Figure a, the SSE-ASLIB exhibits a slow voltage drop at 160 °C; notably, the voltage drop is not as rapid as in the LE-LIB.…”

“…As high temperatures accelerate chemical degradation, the marginal voltage drop is also expected in ASLIBs. 21 As shown in Figure 3a, the SSE-ASLIB exhibits a slow voltage drop at 160 °C; notably, the voltage drop is not as rapid as in the LE-LIB. The dimensional stability of the SSE (LPSCl, annealing temperature 550 °C) prevents direct electrical shorting of ASLIBs even at higher temperatures.…”

“…Intensive research on SSE-ASLIBs has been on enhancing their electrochemical performance; however, understanding their operational safety at component and cell levels is still lacking. 21 Therefore, in this work, we present preliminary but essential information about the overall safety behavior of ASLIBs using two SSEs (LPSCl and LPSBI). These two SSEs are used because LPSBI has a higher ionic conductivity and anode stability.…”

Microscopic Degradation Mechanism of Argyrodite-Type Sulfide at the Solid Electrolyte–Cathode Interface

“…Furthermore, Banerjee et al reported the generation of partially oxygen-substituted P­(S/O) x units at the degraded interface of argyrodite-type Li 6 PS 5 Cl/LiNbO 3 -coated LiNi 0.85 Co 0.1 Al 0.05 O 2 using Raman spectroscopy . Ando et al suggested that the P­(S/O) x generation is a decomposed species of Li 6 PS 5 Cl; therefore, the P­(S/O) x unit can be assigned to a new peak. Although Li 3 PO 4 may be formed, we suggest that the main cause of the P–O bond is not likely owing to the absence of Li 3 PO 4 crystal peaks in the ED pattern (Figure ).…”

Defect Strategy in Solid‐State Lithium Batteries

“…Lithium argyrodites, Li 6 PS 5 X (X = Cl, Br, I), which exhibit low cost and high ionic conductivity (above 1 mS cm −1 ) at room temperature, make them a promising group of SSEs. [ 132 ] The Li 6 PS 5 X argyrodite is derived from the archetypal mineral argyrodite (Ag 8 GeS 6 ) with a cubic structure and a space group of F $$\bar{4}$$ 3m . [ 133 ] In the structure of Li 6 PS 5 X, the S atoms occupy 4a and 4c Wyckoff positions and the Li ions occupy 48 h positions.…”