Title: Computational Exploration of the Li-Electrode|Electrolyte Interface in the Presence of a Nanometer Thick Solid-Electrolyte Interphase Layer [Computational exploration of the Li-electrode|electrolyte interface complicated by a nanometer thin solid-electrolyte interphase (SEI) layer]

Abstract

A nanometer thick passivation layer will spontaneously form on Li-metal in battery applications due to electrolyte reduction reactions. This passivation layer in rechargeable batteries must have “selective” transport properties: blocking electrons from attacking the electrolytes, while allowing Li⁺ ion to pass through so the electrochemical reactions can continue. The classical description of the electrochemical reaction, Li⁺ + e → Li⁰, occurring at the Li-metal|electrolyte interface is now complicated by the passivation layer and will reply on the coupling of electronic and ionic degrees of freedom in the layer. We consider the passivation layer, called “solid electrolyte interphase (SEI)”, as “the most important but the least understood in rechargeable Li-ion batteries,” partly due to the lack of understanding of its structure–property relationship. In predictive modeling, starting from the ab initio level, we find that it is an important tool to understand the nanoscale processes and materials properties governing the interfacial charge transfer reaction at the Li-metal|SEI|electrolyte interface. Here, we demonstrate pristine Li-metal surfaces indeed dissolve in organic carbonate electrolytes without the SEI layer. Based on joint modeling and experimental results, we point out that the well-known two-layer structure of SEI also exhibits two different Li⁺ ion transport mechanisms. The SEI hasmore » a porous (organic) outer layer permeable to both Li⁺ and anions (dissolved in electrolyte), and a dense (inorganic) inner layer facilitate only Li⁺ transport. This two-layer/two-mechanism diffusion model suggests only the dense inorganic layer is effective at protecting Li-metal in electrolytes. This model suggests a strategy to deconvolute the structure–property relationships of the SEI by analyzing an idealized SEI composed of major components, such as Li₂CO₃, LiF, Li₂O, and their mixtures. After sorting out the Li+ ion diffusion carriers and their diffusion pathways, we design methods to accelerate the Li⁺ ion conductivity by doping and by using heterogonous structure designs. We will predict the electron tunneling barriers and connect them with measurable first cycle irreversible capacity loss. We note that the SEI not only affects Li⁺ and e^– transport, but it can also impose a potential drop near the Li-metal|SEI interface. Our challenge is to fully describe the electrochemical reactions at the Li^-metal|SEI|electrolyte interface. This will be the subject of ongoing efforts.« less

Authors:

Li, Yunsong ^[1]; Leung, Kevin ^[2]; Qi, Yue ^[1]

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+ Show Author Affiliations

1. Michigan State Univ., East Lansing, MI (United States). Dept. of Chemical Engineering and Materials Science
2. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

Publication Date:

Fri Sep 30 00:00:00 EDT 2016

Research Org.:

Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Energy Frontier Research Centers (EFRC) (United States). Nanostructures for Electrical Energy Storage (NEES)

Sponsoring Org.:

USDOE National Nuclear Security Administration (NNSA); USDOE Office of Science (SC), Basic Energy Sciences (BES)

OSTI Identifier:

1338679

Report Number(s):

SAND2016-7239J
Journal ID: ISSN 0001-4842; 646176

Grant/Contract Number:  

AC04-94AL85000; SC0001160

Resource Type:

Accepted Manuscript

Journal Name:

Accounts of Chemical Research

Additional Journal Information:

Journal Volume: 49; Journal Issue: 10; Journal ID: ISSN 0001-4842

Publisher:

American Chemical Society

Country of Publication:

United States

Language:

English

Subject:

30 DIRECT ENERGY CONVERSION; 36 MATERIALS SCIENCE