期刊
CHEMISTRY OF MATERIALS
卷 32, 期 5, 页码 2070-2077出版社
AMER CHEMICAL SOC
DOI: 10.1021/acs.chemmater.9b05164
关键词
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资金
- NASA Space Technology Research Fellowship (NSTRF) [80NSSC17K0089]
The electrochemistry of lithium-sulfur (Li-S) batteries is heavily reliant on the structure and dynamics of lithium polysulfides, which dissolve into the liquid electrolyte and mediate the electro-chemical conversion process during operation. This behavior is considerably distinct from the widely used lithium-ion batteries, necessitating new mechanistic insights to fully understand the electrochemical phenomena. Testing at low-temperature conditions presents a unique opportunity to glean new insights into the chemistry in kinetically constrained environments. Under such conditions, despite the low freezing point and favorable ionic conductivity of the glyme-based electrolyte, Li-S batteries exhibit counter-intuitively poor performance. Here, we show that beyond just existing in single-molecule conformations, lithium polysulfides tend to cluster and aggregate in solution, particularly at low-temperature conditions, which subsequently constrains the kinetics of electro-chemical conversion. Energetics and coordination implications of this behavior are extended toward a new framework for understanding the solution coordination dynamics of dissolved lithium species. Based on this framework, a favorable strongly bound lithium salt is introduced in the Li-S electrolyte to disrupt polysulfide clustered networks, enabling substantially enhanced low-temperature electrochemical performance. More broadly, this mechanistic insight heightens our understanding of polysulfide chemistry irrespective of temperature, confirming the link between the solution conformation of active material and electrochemical behavior.
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