Unraveling the role of LiODFB salt as a SEI-forming additive for sodium-ion battery
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ORIGINAL PAPER
Unraveling the role of LiODFB salt as a SEI-forming additive for sodium-ion battery Qimeng Zhang 1,2 & Zhixing Wang 1,2 & Xinhai Li 1,2 & Huajun Guo 1,2 & Jiexi Wang 1,2 & Guochun Yan 1,2 Received: 4 August 2020 / Revised: 28 October 2020 / Accepted: 17 November 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The sodium-ion battery is a strong candidate for the large-scale energy storage device due to its low cost and abundant resources. However, the severe self-discharge issue, which is rooted in the dissolution of the solid-electrolyte interphase (SEI) film in the sodium-ion battery, impedes its practical application. Thus, the central question is how to build a stable SEI film onto the electrode surface. Here, we propose and experimentally demonstrate a LiF-rich SEI film at the surface of hard carbon (HC) anode in sodium-ion battery, which is generated by adding lithium difluoro(oxalate)borate (LiODFB) additive into the electrolyte of 1 M NaPF6 in EC:DMC (1:1 in volume ratio). The X-ray photoelectron spectroscopy (XPS) and electron microscopy (SEM and TEM) results confirm that we obtain the LiF-rich SEI film at the HC electrode surface, which grows up with the increasing of the concentration of added LiODFB additive. But it blocks the transmission of Na ions into HC as evidenced by the initial galvanostatic charge/discharge, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) results. Although this work shows a negative result, it denies the possibility of using the lithium compounds with lower solubility as SEI components for Na-ion battery since it allows to transfer the lithium ions rather than the Na ions. Keywords LiODFB . Electrolyte additive . Sodium-ion battery . SEI film
Introduction Rechargeable lithium-ion batteries have been developed rapidly in the last three decades, on account of its incomparable advantages of high energy density and long service life, which have been widely used in portable electronic devices and electric vehicles [1–6]. However, the large-scale application of lithium-ion batteries has been limited due to the uneven distribution and shortage of lithium resources worldwide. Sodium is similar with lithium in chemical properties but abundant reserves; thus, sodium-ion batteries with low cost and excellent electrochemical performance have broad prospects for large-scale energy storage applications [7–13].
* Guochun Yan [email protected] 1
School of Metallurgy & Environment, Central South University, Changsha 410083, China
2
Engineering Research Center of the Ministry of Education for Advanced Battery Materials, Central South University, Changsha 410083, China
Long-term research on lithium-ion batteries has demonstrated that the solid-electrolyte interphase (SEI) formed on the electrode surface plays an irreplaceable role in the electrochemical performance of lithium-ion batteries. A stable SEI film is insoluble into the electrolyte, which can prevent the cointercalation of solvent molecules into anode and avoid
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