Effects of transition metal cation additives on the passivation of lithium metal anode in Li–S batteries

The effect of additives of transition metal cations (Zn2+, Cu2+, Co2+, Ni2+, and Mn 2+) on the passivation of lithium metal anode in Li–S batteries was investigated. The effects of transition cation additives on improving rate capability and Coulombic efficiency were observed in the following order:...

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Bibliographic Details
Published in:Electrochimica acta 2019-10, Vol.319, p.511-517
Main Authors: Zeng, Wenduo, Cheng, Mark Ming-Cheng, Ng, Simon Ka-Yuen
Format: Article
Language:English
Subjects:
Accumulation
Additives
Anode effect
Cations
Cobalt
Copper
Electrolytes
Lithium
Lithium metal anode
Lithium sulfur battery
Manganese
Metal ions
Metal sulfides
Microbalances
Morphology
Nickel
Nonaqueous electrolytes
Organic chemistry
Passivation
Passivity
Protective coatings
Quartz crystals
SEI
Solid electrolytes
Surface stability
Transition metal cation
Transition metals
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Summary:The effect of additives of transition metal cations (Zn2+, Cu2+, Co2+, Ni2+, and Mn 2+) on the passivation of lithium metal anode in Li–S batteries was investigated. The effects of transition cation additives on improving rate capability and Coulombic efficiency were observed in the following order: Zn2+ > Cu2+ > Co2+ > Ni2+ > Mn2+ > no salt. With Zn additives, less-accumulation of sulfur and smoother surfaces were observed using Scanning Electron Microscope (SEM) compared to that without additives. The result is consistent with Electrochemical Quartz Crystal Microbalance (EQCM) measurement, where less increase in mass changes of the anode for Zn additive as compared to Cu and no additive. The findings can be attributed to transition metal sulfides deposited on lithium surface cooperate with lithium sulfide and electrolyte decomposition product resulting in a smoother and more robust solid electrolyte interphase (SEI) films. The enhanced homogeneity of passivation layer greatly hinders the parasitic reactions between lithium metal and polysulfides as well as organic electrolyte, reducing the loss of active material and improving Coulombic efficiency. On the other hand, the uniform and mechanically strong SEI film introduces less undesired lithium plating and further accumulation on active sites, which significantly enhance the long-term stability due to improved surface morphology and chemistry. The results of this study provide a facile method of in-situ chemical formation of passivation layer protecting the lithium metal in batteries.
ISSN:0013-4686
1873-3859
DOI:10.1016/j.electacta.2019.06.177