Dynamic observation of reversible lithium storage phenomena in hybrid supercapacitor devices

Guan Min Huang, Tsung Chun Tsai, Chun Wei Huang, Nagesh Kumar, Tseung-Yuen Tseng, Wen-Wei Wu*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

10 Scopus citations


Carbonaceous composites have attracted much attention as electrode materials for hybrid supercapacitors. Additionally, transition metal oxides, such as Co 3 O 4 , have high specific capacitance in the charging/discharging process. Here, we investigated the lithium storage mechanism of Co 3 O 4 /CNTs material via in situ transmission electron microscopy (TEM). Additionally, we analyzed the structure and composition of the anode material by high-resolution TEM, electron diffraction, energy dispersive spectroscopy (EDS) and electron energy loss spectroscopy (EELS). Using our unique in situ experimental setup that employs colloidal electrolyte, we elucidate two different mechanisms during operation, including the electrochemical reaction (battery-type) and ions intercalation (supercapacitor-type) of the electrode material. The cube-like Co 3 O 4 nanoparticles were converted to Co nanograins dispersed in the Li 2 O matrix after the first charging cycle. Subsequent cycles presented a reversible reaction between Co/Li 2 O and CoO/Li 2 O. Furthermore, the porous structure of the CNTs and conservation of the Li 2 O matrix allow for the excellent ability to accommodate tremendous volume expansion, which enhances the life of hybrid supercapacitors. Our observations not only provide direct evidence of the electrochemical behavior but also improve the structure to promote enhanced performance for the application of hybrid supercapacitors.

Original languageEnglish
Pages (from-to)494-500
Number of pages7
JournalNano Energy
StatePublished - 1 Nov 2017


  • Co O /CNTs
  • Electrochemical reaction
  • Hybrid supercapacitor
  • In situ TEM
  • Reversible lithium storage

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