Storage of Lithium Metal: The Role of the Native Passivation Layer for the Anode Interface Resistance in Solid State Batteries

Abstract

To overcome current challenges of lithium metal anodes (LMAs), which hinder their wide industrial application, the chemical composition of the lithium metal surface is an important factor. Due to its high reactivity and depending on the pre-treatment during processing, lithium is covered with a passivation layer composed of mainly Li 2 CO 3 , LiOH, and Li 2 O, what is mostly neglected in later electrochemical studies. Here, we investigate the effect of storage time and conditions on the surface passivation layer of commercial lithium foils, based on lithium surface characterization with X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry, finding that only sealed pouch bags can prevent lithium surface changes effectively. Otherwise, the passivation layer thickness increases steadily, even in gloveboxes with a low degree of contaminations. Testing the stored lithium foils in solid-state batteries with LLZO as model solid electrolyte, it is demonstrated that the solid electrolyte roughness and the applied pressure have a huge impact on the obtained impedance. While the passivation layer has no major effect on the interface resistance with a rough LLZO pellet and at high pressure, it clearly affects the interface resistance with smoother LLZO surfaces and at lower pressure. Consequently, the lithium passivation layer may hinder the application of the LMA in a solid-state battery what we discuss in depth. By reactivity experiments with model lithium surfaces, we show that water residuals are the main reason for the aging of lithium foil in gloveboxes. Additionally, nitrogen reacts with fresh lithium surfaces and lithium foils with an incomplete or damaged passivation layer. The results demonstrate that storage conditions are important factors for the surface state of lithium metal and consequently for the application as an anode material.

Interplay of Dynamic Constriction and Interface Morphology between Reversible Metal Anode and Solid Electrolyte in Solid State Batteries

“…Pores, however, are not necessarily required to cause dynamic current constriction. The continuous formation of a spatially heterogeneous insulating layer such as a highly resistive SEI at the interface can also lead to current constriction . The same holds true for the time-dependent depletion of charge carriers at the interface due to the finite diffusion coefficient of the electrode material. ,, Hence, it is worth knowing how different (pore) permittivities ε Int and pore depths δ Int may affect the dynamic constriction phenomenon.…”

Pre‐Lithiation of Silicon Anodes by Thermal Evaporation of Lithium for Boosting the Energy Density of Lithium Ion Cells

“…Therefore CO 2 reacts with Li forming Li 2 CO 3 and thus transforms to Li 2 C 2 . [28] The pre-lithiated Si electrodes were then further examined via X-ray photoelectron spectroscopy (XPS) with an Ar + sputter depth profiling to provide an overview of the lithiation depth (Figure 3a,b). The top surface of both electrodes was covered by a thin layer of Li which will serve as Li metal anode during electrochemical operation.…”

Air/Water Stability Problems and Solutions for Lithium Batteries

“…Sulfide ASSBs are regarded to be one of the most promising energy storage technologies due to their higher safety and ionic conductivity [180][181][182][183][184] However, the poor air/water stability of Ni-rich cathode, sulfide SE, and LMA in sulfide ASSBs system makes them extremely costly and complicated in production, storage, transportation, and battery assembly processes, which seriously hinders the practical production and application of high specific energy sulfide all-solidstate batteries [14,15,28,[185][186][187]. Therefore, solving the air/water instability of Ni-rich cathode, sulfide SE, and Energy Material Advances LMA is crucial for the development of sulfide ASSBs.…”