Origin of Outstanding Stability in the Lithium Solid Electrolyte Materials: Insights from Thermodynamic Analyses Based on First-Principles Calculations

Abstract

First-principles calculations were performed to investigate the electrochemical stability of lithium solid electrolyte materials in all-solid-state Li-ion batteries. The common solid electrolytes were found to have a limited electrochemical window. Our results suggest that the outstanding stability of the solid electrolyte materials is not thermodynamically intrinsic but is originated from kinetic stabilizations. The sluggish kinetics of the decomposition reactions cause a high overpotential leading to a nominally wide electrochemical window observed in many experiments. The decomposition products, similar to the solid-electrolyte-interphases, mitigate the extreme chemical potential from the electrodes and protect the solid electrolyte from further decompositions. With the aid of the first-principles calculations, we revealed the passivation mechanism of these decomposition interphases and quantified the extensions of the electrochemical window from the interphases. We also found that the artificial coating layers applied at the solid electrolyte and electrode interfaces have a similar effect of passivating the solid electrolyte. Our newly gained understanding provided general principles for developing solid electrolyte materials with enhanced stability and for engineering interfaces in all-solid-state Li-ion batteries.

Ion dynamics in solid electrolytes for lithium batteries

“…The formation of such layers, which in most cases consist of decomposition products of the electrolyte, depend on the electrochemical stability of the ion conductor. Many electrolytes known are unstable against Li metal [81][82][83][84]. If high-voltage cathode materials are used to increase the power and energy density of the system, the electrolyte has to withstand potentials as a high as 5 V. Although electrochemical stability of solid electrolytes has been shown to be much better than that of liquid organic blends [84], the long-term stability of a given solid at high cathode potentials or being in contact with Li metal is still one of the white areas future research has to tackle.…”

“…Many electrolytes known are unstable against Li metal [81][82][83][84]. If high-voltage cathode materials are used to increase the power and energy density of the system, the electrolyte has to withstand potentials as a high as 5 V. Although electrochemical stability of solid electrolytes has been shown to be much better than that of liquid organic blends [84], the long-term stability of a given solid at high cathode potentials or being in contact with Li metal is still one of the white areas future research has to tackle. Placing a very thin, artificial interlayer such as crystalline (or amorphous) LiAlO 2 , LiTaO 3 , LiNbO 3 or even Al 2 O 3 [85] at the cathode-electrolyte interface may increase chemical and electrochemical stability [21,79,86,87].…”

Novel Solid Electrolytes for Li-Ion Batteries: A Perspective from Electron Microscopy Studies

“…The stable and conductive electrode/electrolyte interface is a prerequisite for the long-term operation of solid electrolytebased batteries (Zhu et al, 2015(Zhu et al, & 2016Richards et al, 2016). Nevertheless, due to the absence of a mechanistic understanding to guide the rational improvement, it is still very difficult to form such interfaces.…”

“…First, their ionic conductivity is typically low, preventing a fast charge and discharge (Takada, 2013;Wang et al, 2015). Second, forming a stable conductive interface between the solid electrolyte and electrode is difficult (Zhu et al, 2015(Zhu et al, & 2016Richards et al, 2016). Overcoming the first challenge requires a mechanistic understanding of the interplay between Li migration and the atomic framework of the material.…”

Compositional effect investigation by addition PEG, PEO plasticiser of LiBOB based solid polymer electrolyte for lithium ion batteries

“…My research will focus on developing polymer electrolytes for rechargeable batteries. Solid electrolytes conduct lithium ions at room temperature and can potentially replace conventional organic electrolytes, which are flammable and toxic [3]. Solid electrolyte provide advantages in terms of simplicity of manufacture design, no corrosive or explosive liquids can leak out, internal short-circuits are less likely and operational safety, but typically have conductivities that are lower than liquid electrolytes.…”