Editors' Choice—Understanding Chemical Stability Issues between Different Solid Electrolytes in All-Solid-State Batteries

Abstract

Sulfide-based solid electrolytes (SE) are quite attractive for application in all-solid-state batteries (ASSB) due to their high ionic conductivities and low grain boundary resistance. However, limited chemical and electrochemical stability demands for protection on both cathode and anode side. One promising concept to prevent unwanted reactions and simultaneously improve interfacial contacting at the anode side consists in applying a thin polymer film as interlayer between Li metal and the SE. In the present study, we investigated the combination of polyethylene oxide (PEO) based polymer films with the sulfide-based SE Li 10 SnP 2 S 12 (LSPS). We analyzed their compatibility using both electrochemical and chemical techniques. A steady increase in the cell resistance during calendar aging indicated decomposition reactions at the interfaces. By means of X-ray photoelectron spectroscopy and further analytical methods, the formation of polysulfides, P-[S] n-P like bridged PS 4 3− units and sulfite, SO 3 2− , was demonstrated. We critically discuss potential reasons and propose a plausible mechanism for the degradation of LSPS with PEO. The main objective of this paper is to highlight the importance of understanding interfaces in ASSBs not only from an electrochemical perspective, but also from a chemical point of view.

From Liquid- to Solid-State Batteries: Ion Transfer Kinetics of Heteroionic Interfaces

“…Therefore, surface sensitive methods like XPS or ToF-SIMS are useful tools to identify surface species and possibly surface contaminants. Coupling these methods with (four-point) EIS measurements is a good starting point to get a deeper understanding of the occurring (electro)chemistry at the PE/SE interface [67,71]. In the case of chemically non-stable PE/SE interfaces, another interesting aspect is the chemical cross-talk between the PE/SE interface and the electrode/electrolyte interface as decomposition products might dissolve in the PE and move to the electrode.…”

“…Besides oxide-based SEs, thiophosphate-based SEs attracted increasing attention in the last years. In a recently published work, the interface between Li 10 SnP 2 S 12 (LSPS) and dry-processed PEO 15 :LiTFSI was investigated [71]. The formation of polysulfides ( S 2− n ), sulfites ( SO 3 2− ) and P−[S] n −P-type bridged PS 4…”

Pressure effects on sulfide electrolytes for all solid-state batteries

“…12,13 However, the effect of operating stack pressure on this ionic conductivity also needs to be characterized. 14,15 This may explain the large differences in electrochemical measurements in the literature for the same solid electrolyte material.…”

Polymer-based hybrid battery electrolytes: theoretical insights, recent advances and challenges

“…[144][145][146] Indeed, Li 10 SnP 2 S 12 has recently shown to be unstable with PEO-LiTFSI electrolyte. 147 It has been speculated that degradation reactions starts with polymerization of PS 26 llers have been demonstrated to be benecial for the effective ionic transport of the resulting composites. The major transport pathway in the LGPS-PEO composite has been identied to be at the solid/polymer interfaces, again highlighting the importance of the rationally designed composite structure.…”