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Evolution of the electrochemical interface in sodium ion batteries with ether electrolytes.

ABSTRACT: Ether based electrolytes have surfaced as alternatives to conventional carbonates allowing for enhanced electrochemical performance of sodium-ion batteries; however, the primary source of the improvement remains poorly understood. Here we show that coupling titanium dioxide and other anode materials with diglyme does enable higher efficiency and reversible capacity than those for the combination involving ester electrolytes. Importantly, the electrolyte dependent performance is revealed to be the result of the different structural evolution induced by a varied sodiation depth. A suit of characterizations show that the energy barrier to charge transfer at the interface between electrolyte and electrode is the factor that dominates the interfacial electrochemical characteristics and therefore the energy storage properties. Our study proposes a reliable parameter to assess the intricate sodiation dynamics in sodium-ion batteries and could guide the design of aprotic electrolytes for next generation rechargeable batteries.

SUBMITTER: Li K

PROVIDER: S-EPMC6374418 | biostudies-literature | 2019 Feb

REPOSITORIES: biostudies-literature

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Evolution of the electrochemical interface in sodium ion batteries with ether electrolytes.

Li Kaikai K Zhang Jun J Lin Dongmei D Wang Da-Wei DW Li Baohua B Lv Wei W Sun Sheng S He Yan-Bing YB Kang Feiyu F Yang Quan-Hong QH Zhou Limin L Zhang Tong-Yi TY

Nature communications 20190213 1

Ether based electrolytes have surfaced as alternatives to conventional carbonates allowing for enhanced electrochemical performance of sodium-ion batteries; however, the primary source of the improvement remains poorly understood. Here we show that coupling titanium dioxide and other anode materials with diglyme does enable higher efficiency and reversible capacity than those for the combination involving ester electrolytes. Importantly, the electrolyte dependent performance is revealed to be th ...[more]

PMID: 30760713

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Project description:Dual-ion batteries (DIBs) generally operate beyond 4.7 V vs Li+/Li0 and rely on the intercalation of both cations and anions in graphite electrodes. Major challenges facing the development of DIBs are linked to electrolyte decomposition at the cathode-electrolyte interface (CEI), graphite exfoliation, and corrosion of Al current collectors. In this work, X-ray photoelectron spectroscopy (XPS) is employed to gain a broad understanding of the nature and dynamics of the CEI built on anion-intercalated graphite cycled both in highly concentrated electrolytes (HCEs) of common lithium salts (LiPF6, LiFSI, and LiTFSI) in carbonate solvents and in a typical ionic liquid. Though Al metal current collectors were adequately stable in all HCEs, the Coulombic efficiency was substantially higher for HCEs based on LiFSI and LiTFSI salts. Specific capacities ranging from 80 to 100 mAh g-1 were achieved with a Coulombic efficiency above 90% over extended cycling, but cells with LiPF6-based electrolytes were characterized by <70% Coulombic efficiency and specific capacities of merely ca. 60 mAh g-1. The poor performance in LiPF6-containing electrolytes is indicative of the continual buildup of decomposition products at the interface due to oxidation, forming a thick interfacial layer rich in LixPFy, POxFy, LixPOyFz, and organic carbonates as evidenced by XPS. In contrast, insights from XPS analyses suggested that anion intercalation and deintercalation processes in the range from 3 to 5.1 V give rise to scant or extremely thin surface layers on graphite electrodes cycled in LiFSI- and LiTFSI-containing HCEs, even allowing for probing anions intercalated in the near-surface bulk. In addition, ex situ Raman, SEM and TEM characterizations revealed the presence of a thick coating on graphite particles cycled in LiPF6-based electrolytes regardless of salt concentration, while hardly any surface film was observed in the case of concentrated LiFSI and LiTFSI electrolytes.

Dataset Information

Evolution of the electrochemical interface in sodium ion batteries with ether electrolytes.

Publications

Evolution of the electrochemical interface in sodium ion batteries with ether electrolytes.

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