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First-Principles Insights on the Formation Mechanism of Innermost Layers of Solid Electrolyte Interphases on Carbon Anodes for Lithium-Ion Batteries.

ABSTRACT: A solid electrolyte interphase (SEI) plays an essential role in the functionality and service life of ion batteries, where the structure and formation mechanism are still in the midst. Here, we investigate the initial decomposition and reactions of ethylene carbonate (EC) on the surface of a graphite anode using first-principles calculations. EC initially decomposes via the homolytic ring opening with the product of radical anion CH₂CH₂OCO₂^-. Bonding with Li, it forms a co-plane structure of CH₂CH₂OCO₂Li, with a binding energy of 1.35 eV. The adsorption energy is -0.91 eV and -0.24 eV on the graphite zigzag edge surface and basal surface, respectively. Two CH₂CH₂OCO₂Li molecules react to form a two-head structure of lithium ethylene dicarbonate (CH₂OCO₂Li)₂, namely LEDC, which further forms a network preferring zigzag edge surfaces. Our results suggest that the first and innermost layers of the solid electrolyte interphase are CH₂CH₂OCO₂Li sticking and networking on the zigzag edges of the surfaces of graphite anodes.

SUBMITTER: Peng Q

PROVIDER: S-EPMC9607018 | biostudies-literature | 2022 Oct

REPOSITORIES: biostudies-literature

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First-Principles Insights on the Formation Mechanism of Innermost Layers of Solid Electrolyte Interphases on Carbon Anodes for Lithium-Ion Batteries.

Peng Qing Q

Nanomaterials (Basel, Switzerland) 20221018 20

A solid electrolyte interphase (SEI) plays an essential role in the functionality and service life of ion batteries, where the structure and formation mechanism are still in the midst. Here, we investigate the initial decomposition and reactions of ethylene carbonate (EC) on the surface of a graphite anode using first-principles calculations. EC initially decomposes via the homolytic ring opening with the product of radical anion CH2CH2OCO2-. Bonding w ...[more]

PMID: 36296843

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Project description:The formation of a solid electrolyte interphase (SEI) between the anode surface and the electrolyte of lithium-ion batteries (LIBs) has been considered to be the most important yet the least understood issue of LIBs. To further our understanding in this regard, the density functional theory (DFT) B3PW91/6-311++G(3df,3pd) together with the implicit solvent model and the transition state theory were used for the first time to comprehensively explore the electroreduction mechanism of a novel additive, 4-chloromethyl-1,3,2-dioxathiolane-2-oxide (CMDO), and a few other solvents and additives, such as ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), fluoroethylene carbonate (FEC), and even ethylene sulfite (ES), for comparison. The one-electron reduction potential of Li+-coordinated compounds Li+(X) for forming decomposition precursors [c-Li+(X˙-)] decreases in the following sequence: CMDO (1.9-2.2 V vs. Li+/Li) ∼ ES(1.9 V) > FEC (0.7 V) > EC (0.47 V) > PC (0.45 V) > DMC (0.38 V); this implies that CMDO is reduced prior to other solvents or additives in the mixture. Although the ring opening of [c-Li+(CMDO˙-)] is the least kinetically favorable, as reflected by the highest energy barrier (E a), i.e., CMDO (18.8-22.9 kcal mol-1) ∼ ES (23.4) > FEC (16.2) > PC (12.5) > EC (11.2) > DMC (8.0), CMDO still shows the highest overall reaction rate constant (∼1053 s-1) for forming an open ring radical [o-Li+(CMDO˙)-]. In addition, the termination reaction of [o-Li+(CMDO˙)-] for forming LiCl is thermodynamically more favorable than that of Li2SO3 or organic disulfite (LiSO3)2-R, which supports the experimental observation that the halogen-containing LiF or LiCl additives are predominant over all other halogen-containing species in the SEI layer. Moreover, the hybrid model by including the second solvation shell of Li+ via a supercluster [(CMDO)Li+(PC)2](PC)9 and the implicit solvent model (SMD) can result in a reduction potential (∼1.7 V) that is in excellent agreement with the experimental reduction peak.

Dataset Information

First-Principles Insights on the Formation Mechanism of Innermost Layers of Solid Electrolyte Interphases on Carbon Anodes for Lithium-Ion Batteries.

Publications

First-Principles Insights on the Formation Mechanism of Innermost Layers of Solid Electrolyte Interphases on Carbon Anodes for Lithium-Ion Batteries.

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