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Influence of the Morphology of Lithiated Copper(I) Sulfides with the Formal Composition “Li 2 Cu 4 S 3 ” on Their Stability in Electrochemical Cycling
Author(s) -
Eichhöfer Andreas,
Sommer Heino,
Andrushko Vasyl,
Indris Sylvio,
Malik Sharali
Publication year - 2013
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201201099
Subject(s) - diglyme , chemistry , copper , lithium (medication) , electrochemistry , dimethoxyethane , inorganic chemistry , electrolyte , thermal decomposition , thermal stability , copper sulfide , chemical engineering , solvent , organic chemistry , electrode , medicine , engineering , endocrinology
Two different approaches were developed for the synthesis of lithiated copper(I) sulfide with the formal composition “Li 2 Cu 4 S 3 ”. In the first approach, thiolato‐bridged copper cluster complexes [Li(dme) 3 ] 2 [Cu 4 (SPh) 6 ] (dme = dimethoxyethane) and [Li(diglyme) 2 ] 2 [Cu 4 (SPh) 6 ] (diglyme = diethylene glycol dimethyl ether) were decomposed/thermolized at 400 °C to form the lithiated copper(I) sulfides upon cleavage of the ether ligands and 3 equiv. of SPh 2 . In the second approach, Li 2 S and 2 equiv. of Cu 2 S were allowed to react in quartz ampoules sealed under vacuum at 400 °C. The as‐synthesized powders reveal complex room‐temperature XRD powder patterns with clear differences between the two materials. Scanning electron microscopy reveals that the material synthesized by thermolysis of the cluster material is composed of a porous network of agglomerated nanoparticles, whereas the other material is composed of compact micron‐sized crystals. The initial specific capacities for galvanostatic charging and discharging of nanostructured and porous “Li 2 Cu 4 S 3 ” cathodes vs. lithium metal anodes in a limited range between 1.7 and 3 V are ca. 143 A h kg –1 . This is 97.3 % of the theoretical value for the exchange of two lithium ions and 5 % higher than for the compact material at ca. 136 A h kg –1 . However, we observed that upon prolonged cycling the capacity of the nanostructured and porous “Li 2 Cu 4 S 3 ” fades much faster than that of the compact material. This means that after 100 cycles the nanostructured and porous material had faded by 67 %, whereas the compact material still reaches a specific capacity of 109 A h kg –1 .