Interface Stability in Solid-State Batteries

Abstract

Development of high conductivity solid-state electrolytes for lithium ion batteries has proceeded rapidly in recent years, but incorporating these new materials into high-performing batteries has proven difficult. Interfacial resistance is now the limiting factor in many systems, but the exact mechanisms of this resistance have not been fully explained - in part because experimental evaluation of the interface can be very difficult. In this work, we develop a computational methodology to examine the thermodynamics of formation of resistive interfacial phases. The predicted interfacial phase formation is well correlated with experimental interfacial observations and battery performance. We calculate that thiophosphate electrolytes have especially high reactivity with high voltage cathodes and a narrow electrochemical stability window. We also find that a number of known electrolytes are not inherently stable but react in situ with the electrode to form passivating but ionically conducting barrier layers. As a reference for experimentalists, we tabulate the stability and expected decomposition products for a wide range of electrolyte, coating, and electrode materials including a number of high-performing combinations that have not yet been attempted experimentally.

Lithium Superionic Conductor Li9.42Si1.02P2.1S9.96O2.04 with Li10GeP2S12-Type Structure in the Li2S–P2S5–SiO2 Pseudoternary System: Synthesis, Electrochemical Properties, and Structure–Composition Relationships

“…In addition, the shapes of the CV curves at 3-5 V did not change significantly over five cycles, indicating electrochemical stability with respect to oxidation when in contact with cathode materials having a high electrochemical potential (4-5 V vs. Li/Li + ). This experimentally observable stability toward oxidation is considered due to formation of a passivation layer between a solid electrolyte and electrode (Han et al, 2015;Richards et al, 2016). Cathodic and anodic currents were observed near 0 V (vs. Li + /Li), these were partly owing to the lithium deposition reaction (Li + + e − → Li) and the dissolution reaction (Li → Li + + e − ), respectively.…”

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.…”

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.…”

“…Beyond these experimentally observed reaction layers, highly localized interfacial decomposition at the solid electrolyte and electrode interfaces was frequently speculated, although they show a certain degree of stability in electrochemical measurements (Zhu et al, 2015(Zhu et al, & 2016Richards et al, 2016). However, most of such speculations are proposed based on theoretical calculations.…”

“…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.…”