Di-ureasil hybrids doped with LiBF4: attractive candidates as electrolytes for "Smart Windows"

The sol-gel process has been used to prepare hybrid electrolytes composed of a poly(oxyethylene) (POE)/siloxane hybrid network doped with lithium tetrafluoroborate (LiBF4) with compositions of n between ∞ and 2.5. In this context the lithium salt concentration is expressed in terms of the number of...

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Detalhes bibliográficos
Autor principal: Barbosa, P. C. (author)
Outros Autores: Fernandes, M. (author), Silva, Maria Manuela (author), Smith, Michael John (author), Vilela, Sérgio M. F. (author), Gonçalves, A. (author), Olveira, M. C. (author), Fortunato, E. (author), Rego, R. (author), Zea Bermudez, V. de (author)
Formato: article
Idioma:eng
Publicado em: 2011
Assuntos:
Solid polymer electrolyte
Ionic conductivity
Thermal analysis
Electrocehmical satbility
Organic/inorganic hybrid electrolytes
Lithium trifluoroborate
Cyclic voltammetry
Electrochromic device
lithium tetrafluoroborate
Science & Technology
Texto completo:http://hdl.handle.net/1822/13611
País:Portugal
Oai:oai:repositorium.sdum.uminho.pt:1822/13611
Descrição
Resumo:The sol-gel process has been used to prepare hybrid electrolytes composed of a poly(oxyethylene) (POE)/siloxane hybrid network doped with lithium tetrafluoroborate (LiBF4) with compositions of n between ∞ and 2.5. In this context the lithium salt concentration is expressed in terms of the number of oxyethylene units in the organic component of the network per Li+ ion. Electrolyte samples with n ≥ 20 are thermally stable up to approximately 250 ºC. All the materials synthesized are semi-crystalline: in the composition range n ≥ 15 free crystalline POE exists and at 60 ≥ n ≥ 2.5 evidence of the presence of a crystalline POE/LiBF4 compound has been found. At n = 2.5 this latter crystalline phase coexists with free salt. The room temperature conductivity maximum of this electrolyte system is located at n = 10 (1.5x10-5 S cm-1 at 22 ºC). The electrochemical stability domain of the sample with n = 15 spans about 5.5 V versus Li/Li+. This new series of materials represents a promising alternative to the LiTFSI- and LiClO4-doped POE and POE/siloxane analogues. Preliminary tests performed with a prototype electrochromic device (ECD) comprising the sample with n = 8 as electrolyte and WO3 as cathodically coloring layer are extremely encouraging. The device exhibits switching time around 50 s, an optical density change of 0.13, open circuit memory of about 4 months and high coloration efficiency (106 cm2C-1 in the 3rd cycle).

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