Pressure-Driven and Creep-Enabled Interface Evolution in Sodium Metal Batteries

Abstract

All-solid-state batteries (ASSBs) using an alkali metal anode and a solid-state electrolyte (SE) face several problems due to poor physical and electrical contact. Recent experiments have shown that applying a stack pressure can improve the interface contact and suppress void formation. The mechanical properties of Na metal are different from those of Li metal, leading to differences in the mechanisms of the pressure-dependent interface evolution. Herein, we report a three-dimensional time-dependent model for tracking the evolution of interfaces formed between Na metal and Na-β″-alumina SE. Our results show that Na metal contacts more conformally with the SE, providing a lower interfacial resistance, compared with Li metal, assuming equal resistance due to contamination. The differences due to contact elastoplasticity are larger than the differences in metal creep effects. In fact, we show that increased stack pressure can lead to lower creep because the contact is more conformal at high pressures. Our excellent agreement with recent experiments determines an effective hardness of Na in the Na-SE batteries to be 15 MPa. The results further reveal that the pressure dependence of void suppression is dominated by contact elastoplasticity.

Porosity of Solid Electrolyte Interphases on Alkali Metal Electrodes with Liquid Electrolytes

“…Note that the creep due to the pressure buildup in the cell causes the smoother surface of Na upon longer open-circuit potential storage. 39 − 41 …”

“…Considering the fact that increased E a (SEI) over time was observed for both Li-glyme and Na-glyme systems, the observed morphology and thickness of SEIs imply the densification (or compaction) of the SEIs. Note that the creep due to the pressure buildup in the cell causes the smoother surface of Na upon longer open-circuit potential storage. − …”

Recent Advances in Stabilization of Sodium Metal Anode in Contact with Organic Liquid and Solid‐State Electrolytes

“…Kasemchainan et al [ 41 ] suggested that a stacking pressure of 5‐7 MPa can be favorable for Li metal stripping and plating during a steady electrochemical cycling. A 3D time‐dependent model ( Figure 9 a) for tracking the evolution of interfaces formed between Na metal and Na‐β"‐Al 2 O 3 was reported by Zhang et al [ 99 ] The differences due to contact elastoplasticity are larger than the differences in metal creep effects. The increased stack pressure can lead to lower creep due to a more conformal contact at the high pressure.…”

“…Reproduced with permission. [ 99 ] Copyright 2021, American Chemical Society. b) Schematic of the insights into Na + ion transfer at Na/NASICON interface improved by uniaxial compression.…”

“…Figure 9. a) A 3D time-dependent model for tracking the evolution of interfaces formed between Na metal and Na-β"-Al 2 O 3 . Reproduced with permission [99]. Copyright 2021, American Chemical Society.…”