Abstract
The solid-electrolyte interphase (SEI) is crucial to the electrochemical performance of all-solid-state batteries (ASSBs). Theoretical characterization of SEI properties will help understand the origin of interfacial stability (and instability) between solid electrolytes and electrodes. Among solid electrolytes for Lithium (Li)-ion ASSBs, the lithium phosphorus oxynitride (LiPON) is one of the most stable against the metal anode. However, it has been shown that LiPON reacts with metal and forms SEIs. The SEI formation stops after a thin layer is formed, but the mechanism that enables this apparent stabilization is unclear. Thermodynamics underpins the defect formation in materials and, in turn, creation of electronic charge. Materials for energy storage, including solid electrolytes, are no exception to this fundamental process. Here, we computationally evaluate the electronic passivation of SEIs and its role in stabilizing the -LiPON interface. Specifically, we determine the defect and charge carrier concentrations in -LiPON SEIs, including , , , and . The defect and charge carrier concentrations are calculated from defect thermodynamics. We then predict the electronic conductivities of the SEIs under different electrochemical conditions, which correspond to varying potentials to the Li metal anode. Our results reveal that the stoichiometrically abundant and uniformly distributed has expectedly negligible electronic conductivity, while the electronically conducting components, such as and , show preferential distribution in the SEI. We posit that the overall electronically insulating nature of the SEI is responsible for the stability of the -LiPON interface. The computational approach adopted here can be extended to reveal the origin of the interfacial stability in other ASSBs.
- Received 22 March 2022
- Revised 27 June 2022
- Accepted 29 June 2022
DOI:https://doi.org/10.1103/PRXEnergy.1.023004
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.
Published by the American Physical Society
Physics Subject Headings (PhySH)
Popular Summary
All-solid-state batteries (ASSBs) hold promise as a safer and higher-energy-density alternative to state-of-the-art lithium-ion batteries. One of the key challenges in the development of ASSBs is the understanding and control of the interface between the alkali-metal anode and the solid electrolyte, an interface which is often unstable and a source of battery failure. The stability of this interface depends on the properties of the chemically-distinct interlayer that forms at the boundary, known as the solid-electrolyte interphase (SEI).
In this work, the authors study the lithium metal / lithium phosphorous oxynitride () interface, which forms a self-limiting, stable SEI. To understand the origin of this stability, the authors use first-principles calculations to model the electronic conductivity of the components that make up the SEI: , , , and . They find that the majority components of the SEI, and , are electronically insulating under operating conditions, suggesting that the SEI serves as an electronically passivating layer in batteries that limits the decomposition of .
