The metal oxides were derived from lithium metal oxides through the phase transformation of a lithium metal oxide to metal oxide by catalytic delithiation using silesquioxane-coated lithium metal oxide as a precursor. The metal oxide was gradually formed from the surface of the lithium metal oxide contacting with silesquioxane through the phase transformation. Lithium silicate (Li2SiO3) was subsequently formed by the reaction between lithium and silesquioxane. Detailed characterizations were performed using spinel Li4Ti5O12. Li4Ti5O12/TiO2 composites with three identifiable areas: a core (Li4Ti5O12), shell (TiO2), and coating layer (Li2SiO3) were derived by the simple thermal treatment of silesquioxane-coated lithium metal oxide in inert gas. During the thermal treatment, the silesquioxane coating layer was formed owing to the phase transformation of spinel Li4Ti5O12 to anatase TiO2. In addition, it sequentially reacted with lithium while forming an Li2SiO3 coating layer. TiO2 hydrogenation was further induced, which had Ti3+ sites and oxygen vacancies. The Li2SiO3-coated Li4Ti5O12/TiO2 composite exhibited significantly improved specific capacity, rate capability, and cycling stability, in comparison to pristine Li4Ti5O12. The improved electrochemical properties of the composite can be attributed to the following factors. (1) The phase transformation of spinel Li4Ti5O12 to anatase TiO2 increased the specific capacity of the composite because anatase TiO2 has a higher theoretical capacity than spinel Li4Ti5O12. (2) TiO2 hydrogenation increased the electronic and ionic conductivities by introducing Ti3+ sites and oxygen vacancies. (3) The Li2SiO3 coating layer suppressed gas production by protecting the composite surface from the electrolytes.
|Number of pages||10|
|Journal||Energy Storage Materials|
|Publication status||Published - 2020 Mar|
Bibliographical noteFunding Information:
This research was supported by the Technology Innovation Program ( 20004958 , Development of ultra-high performance supercapacitor and high power module) funded by the Ministry of Trade, Industry & Energy (MOTIE, Korea) . This work was also supported by the Industry Technology Development Program ( 10080540 , Development of filmtype flexible supercapacitor with microstructured electrodes based on nanomaterials) funded by the Ministry of Trade, Industry & Energy (MOTIE, Korea) .
All Science Journal Classification (ASJC) codes
- Renewable Energy, Sustainability and the Environment
- Materials Science(all)
- Energy Engineering and Power Technology