Mechanistic insight into the performance enhancement of Si anode of a lithium-ion battery with a fluoroethylene carbonat
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RESEARCH ARTICLE
Mechanistic insight into the performance enhancement of Si anode of a lithium-ion battery with a fluoroethylene carbonate electrolyte additive Anil D. Pathak1 · Kousik Samanta2 · Kisor K. Sahu1 · Soobhankar Pati1 Received: 21 June 2020 / Accepted: 14 September 2020 © Springer Nature B.V. 2020
Abstract Silicon anode, even with its theoretically high specific capacity, has only seen a limited commercial adoption in lithium-ion battery (LIB) due to the durability issues. The performance of a silicon anode in a LIB is enhanced when a small amount of fluoroethylene carbonate (FEC) is added to the battery electrolyte. In this article, we analyze the effect of FEC additive on the silicon anode in both the half- and full cell configuration. Electrochemical impedance spectroscopy is used to unravel crucial intrinsic properties of the cell. It detects a fourfold drop in the cell impedance upon addition of FEC. We also employed density functional theory (DFT)-based models to understand and complement the experimental findings. At the DFT level, the solvation energy of L i+ in the ethylene carbonate (EC) electrolyte is − 224.34 kJ mol−1 whereas that in the FEC electrolyte is − 202.96 kJ m ol−1. This implies that the electrolyte with the FEC additive may act as a better carrier + of Li that with the EC additive alone. Graphic abstract
Keywords Silicon · Li-ion battery · Fluoroethylene carbonate (FEC) · Density functional theory (DFT) · Scanning electron microscopy Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10800-020-01484-3) contains supplementary material, which is available to authorized users. Extended author information available on the last page of the article
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1 Introduction Silicon anode has a high theoretical capacity of 3579 mAh g−1, almost 10 times higher than the present-de facto commercial graphite anode in a lithium-ion battery, LIB [1]. One of the main hurdles in integrating a silicon anode in a LIB is the mechanical stability of the solid–electrolyte interface, SEI [2–4]. The SEI is formed on the anode due to the reduction of the organic additive if the anode has lower potential (vs. Li/Li+) compared to the reduction potential of the organic additives in the electrolyte [5]. Both graphite and silicon have lower potential (vs. Li/ Li+) compared to the reduction potential of the ethylene carbonate generally used as an electrolyte additive. Hence SEI is formed in case of both graphite and silicon. However, the SEI formed on graphite is stable compared to the one formed on the silicon because the volume change during lithiation/delithiation cycle is only 10% in graphite compared to 300% in silicon [6–9]. The large volume change induces severe steric strain, which typically leads to the fragmentation of silicon particles and results in an unstable SEI [10]. This re-exposes fresh silicon surface to the electrolyte and a new layer of SEI is formed; resulting in a progressively thicker SEI layer with each progr
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