Key Takeaways & Executive Findings
- •• The succinonitrile-based deep eutectic electrolyte, characterized by strong ion–dipole interactions, can establish an anion-rich Li+ solvation structure while exhibiting high ionic conductivity and Li+ transference number. • Precisely regulating multiple ion–ion, ion–dipole, and dipole–dipole interactions facilitates the transition of the Li+ solvation structure from solvent dominance to anion dominance. • Optical microscopy and Micro-CT analysis can demonstrate that the anion-derived solid electrolyte interphase effectively mitigates the irreversible volume expansion of silicon oxide. • The SiO|LiCoO2 full cells exhibit excellent electrochemical performance in deep eutectic-based electrolytes, presenting an effective strategy for extending the cycle life of SiO anodes.
Abstract
Micrometer-sized silicon oxide (SiO) anodes encounter challenges in large-scale applications due to significant volume expansion during the alloy/de-alloy process. Herein, an innovative deep eutectic electrolyte derived from succinonitrile is introduced to enhance the cycling stability of SiO anodes. Density functional theory calculations validate a robust ion–dipole interaction between lithium ions (Li+) and succinonitrile (SN). The cosolvent fluoroethylene carbonate (FEC) optimizes the Li+ solvation structure in the SN-based electrolyte with its weakly solvating ability. Molecular dynamics simulations investigate the regulating mechanism of ion–dipole and cation–anion interaction. The unique Li+ solvation structure, enriched with FEC and TFSI−, facilitates the formation of an inorganic–organic composite solid electrolyte interphase on SiO anodes. Micro-CT further detects the inhibiting effect on the SiO volume expansion. As a result, the SiO|LiCoO2 full cells exhibit excellent electrochemical performance in deep eutectic-based electrolytes. This work presents an effective strategy for extending the cycle life of SiO anodes by designing a new SN-based deep eutectic electrolyte.
1. Introduction
Given the escalating demand for energy concerns [1–3], developing rechargeable batteries with high-energy density and low cost is more and more imperative [4–6]. Silicon oxide (SiO) [7, 8] is highly suitable for commercial applications owing to its high capacity and processibility [9, 10]. Additionally, the SiO anodes exhibit decreased volume expansion during the charge and discharge cycles in compared to pure silicon [11, 12]. Despite the above advantages [13, 14], the SiO anodes still suffer from some limitations: (i) the low intrinsic electron conductivity; (ii) the irreversible formation of Li2O and lithium silicates; (iii) the residual volume expansion effect. In past years, many efforts primarily focused on mitigating volume expansion through material design [15], surface coating [16], and defect design [17]. Despite significant progress made in material modification studies, the solid–liquid interface compatibility in batteries remains inadequate, primarily attributed to the recurrent cracking tendencies of silicon-based anodes [18, 19]. Further investigation is still required to elucidate the interface reactions for constructing high-strength solid electrolyte interphase (SEI) between the SiO anodes and the electrolyte for long-spanlife lithium-ion batteries [20, 21].
The electrolyte, which plays a crucial role in silicon-based lithium-ion batteries, is essential for ensuring its long-term durability and maintaining SEI stability. In conventional liquid carbonate electrolytes (LE), the Li+ solvation sheath is primarily composed of organic solvent molecules such as ethylene carbonate (EC) and dimethyl carbonate (DMC) [6, 22, 23]. Typically, the decomposition of carbonate solvent molecules is preferentially initiated with a 1.0-M salt concentration in conventional carbonate solvents. This process leads to the formation of rich organic products with subpar mechanical properties, causing continuous electrolyte permeation and the accumulation of a thick SEI layer. The thick and unstable SEI film will aggravate the side reaction between electrolyte and electrode, resulting in further deterioration of electrochemical performance. Hence, optimizing the compatibility between the electrolyte and electrode through adjustments to the intrinsic Li+ solvation structure of the electrolyte holds paramount importance. Inspired by that, C
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Shengwei Dong, Lingfeng Shi, Shenglu Geng, Yanbin Ning, Cong Kang, Yan Zhang, Ziwei Liu, Jiaming Zhu, Zhuomin Qiang, Lin Zhou, Geping Yin, Dalong Li, Tiansheng Mu, Shuaifeng Lou (2024). Breaking Solvation Dominance Effect Enabled by Ion–Dipole Interaction Toward Long-Spanlife Silicon Oxide Anodes in Lithium-Ion Batteries. Nano-Micro Letters. https://doi.org/10.1007/s40820-024-01592-1
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Frequently Asked Questions
What is the main challenge for silicon oxide anodes in lithium-ion batteries?
Micrometer-sized silicon oxide (SiO) anodes face significant volume expansion during the alloy/de-alloy process, which leads to poor cycling stability and limits their large-scale application.
How does the proposed deep eutectic electrolyte improve the performance of SiO anodes?
The succinonitrile-based deep eutectic electrolyte, with strong ion–dipole interactions, establishes an anion-rich Li+ solvation structure. This facilitates the formation of a robust inorganic–organic composite solid electrolyte interphase on SiO anodes, mitigating volume expansion and enhancing cycling stability.
What role does fluoroethylene carbonate (FEC) play in the electrolyte?
FEC acts as a weakly solvating cosolvent that optimizes the Li+ solvation structure in the SN-based electrolyte, promoting the formation of an anion-rich solvation sheath and improving the interphase properties.
What experimental techniques were used to validate the findings?
The study employed density functional theory (DFT) calculations, molecular dynamics (MD) simulations, optical microscopy, and Micro-CT analysis to validate the ion–dipole interactions, solvation structure regulation, and the inhibition of SiO volume expansion.
What is the significance of this work for lithium-ion battery technology?
This work presents an effective strategy for extending the cycle life of SiO anodes by designing a new SN-based deep eutectic electrolyte, offering a promising approach for high-energy-density lithium-ion batteries with improved durability.
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