Effect of Particle Size and Pressure on the Transport Properties of the Fast Ion Conductor t‐Li₇SiPS₈

Abstract

All‐solid‐state batteries promise higher energy and power densities as well as increased safety compared to lithium‐ion batteries by using non‐flammable solid electrolytes and metallic lithium as the anode. Ensuring permanent and close contact between the components and individual particles is crucial for long‐term operation of a solid‐state cell. This study investigates the particle size dependent compression mechanics and ionic conductivity of the mechanically soft thiophosphate solid electrolyte tetragonal Li7SiPS8 (t‐LiSiPS) under pressure. The effect of stack and pelletizing pressure is demonstrated as a powerful tool to influence the microstructure and, hence, ionic conductivity of t‐LiSiPS. Heckel analysis for granular powder compression reveals distinct pressure regimes, which differently impact the Li ion conductivity. The pelletizing process is simulated using the discrete element method followed by finite volume analysis to disentangle the effects of pressure‐dependent microstructure evolution from atomistic activation volume effects. Furthermore, it is found that the relative density of a tablet is a weaker descriptor for the sample's impedance compared to the particle size distribution. The multiscale experimental and theoretical study thus captures both atomistic and microstructural effects of pressure on the ionic conductivity, thus emphasizing the importance of microstructure, particle size distribution and pressure control in solid electrolytes.

First-Principles Study on the Interplay of Strain and State-of-Charge with Li-Ion Diffusion in the Battery Cathode Material LiCoO2

“…A nonzero activation volume serves as an indicator of a disparity between the available free volume within the structure and the volume necessary for efficient ion migration. A positive V a shows that Li + ions need to open up the space for diffusion, as described in previous studies for Li 10 GeP 2 S 12 (+2.17 cm 3 /mol), Na 3 PS 4 (+1.78 cm 3 /mol for high temperature), and t-Li 7 SiPS 8 (+1.7–2.0 cm 3 /mol) . On the other hand, a negative V a , indicating an enhanced ionic diffusivity under increasing pressure, is also observed in certain cases, for example, Ag 3 SI (−2.3 ± 0.4 cm 3 /mol) and Li-β-Al 2 O 3 (−0.7 cm 3 /mol) .…”

Anion Engineering for Stabilizing Li Interstitial Sites in Halide Solid Electrolytes for All-Solid-State Li Batteries

“…For both samples, the gravimetric density and ionic conductivity curves were saturated near 280 MPa, and the curves were almost overlapped in the low-pressure region, implying that oxygen substitution had a marginal effect on compressibility. However, it is noteworthy that the results of those compression experiments can be varied by other factors like particle size . Therefore, an in-depth study using specialized methods such as the indentation test and the speed-of-sound measurement should be dedicated to fully characterize their mechanical property. ,− On the other hand, we observed locally distributed pores more frequently for LZCO pellets than LZC pellets (Figure ).…”

“…However, it is noteworthy that the results of those compression experiments can be varied by other factors like particle size. 34 Therefore, an in-depth study using specialized methods such as the indentation test and the speed-of-sound measurement should be dedicated to fully characterize their mechanical property. 6,35−37 On the other hand, we observed locally distributed pores more frequently for LZCO pellets than LZC pellets (Figure 5).…”

Pressure dependence of ionic conductivity in site disordered lithium superionic argyrodite Li6PS5Br

“…When pressure is applied on Li 6 PS 5 Br, an initial increase in ionic conductivity is observed as the consolidation of the pellet takes place. 42 During the initial increase of the external applied pressure, the gaps between particles are filled and particle–particle contact is enhanced during the pellet formation 33,43 (Fig. 3b).…”