Alternative energy sources have received great attention since traditional energy sources, fossil fuels, are non-renewable and causing critical environmental damage. Rechargeable lithium-ion batteries (LIBs) with high power density, long cycle life and environmental friendliness are of huge interest for application as power supply in electric vehicles and renewable energy storage [1]. However, current wide implementation of LIBs is restricted by several factors, such as a low capacity, instability and toxicity of the electrode materials. Silica (SiO2) is an eco-friendly candidate for the next generation anode materials for high energy density LIBs with a high lithium (Li) storage capacity (1961 mAh g-1 for silica) at a lower cost [2]. However, pure silica has a poor electrical conductivity and suffers from rapid capacity fading due to significant volume changes during charge/discharge. These limitations could be overcome by applying carbon and/or polymer coatings [3] and engineering various hollow nanostructures [4] to increase the conductivity and accommodate the volume changes, respectively [5]. Herein, we propose an innovative chemical free approach to prepare a novel composite anode material combining hollow SiO2nanospheres, carbon nanotube and graphene.
Hollow SiO2 sphere/carbon nanotube/graphene ternary composite was synthesized using sonication (by Ultrasonic Elma S 30) of SiO2 (30 nm, 25%), multi-walled carbon nanotubes (MWNT, 3 %) and graphene (G, 1%) water suspensions in different ratios. Derived mixtures were dried at 50 ºC overnight in vacuum oven (Memmert), and further annealed in air oven (Carbolite) at 500 ºC for 2 h. Finally, SiO2/MWNT/G composites were obtained. Also, for comparison similar composite with single-walled carbon nanotubes (SiO2/SWNT/G) was prepared.
The resulting composites of SiO2/MWNT/G and SiO2/SWNT/G were investigated and characterized by X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). XRD analysis confirmed the amorphous nature of the powders and FTIR spectroscopy identified the existence of Si-O, C-C and C=C bonds in these samples. TGA allowed for determination of the carbon content in the prepared composites. SEM revealed morphology of the samples and distribution of the elements in the composites. The TEM results allowed for characterization of the interior structure of the composite materials. CR2032 coin-type cells were used to evaluate the electrochemical performance of SiO2/MWNT/graphene and SiO2/SWNT/graphene composites in a lithium half-cell structure. The cells were tested galvanostatically in a voltage range of 0.01 – and 3.0 V vs. Li+/Li at a current density of 50 mA g-1 (Neware A602-3000W-CT-A). The further results of these studies will be presented at the conference.
Acknowledgements
This work was supported by the project grant 5097/GF4 “Development of a novel quartz (SiO2) based anode material for Li-ion batteries” from the Ministry of Education and Science of the Republic of Kazakhstan.
References
[1] S. Goriparti, C. Capiglia, J. Power Sources 257 (2014) 421-443
[2] X. Cao, G. Cao, Part. Part. Syst. Charact. 33 (2016) 110-117
[3] X. Cao, G. Cao, J. Mater. Chem. A, 3 (2015) 22739–22749
[4] N. Yan, Scientific Reports (2013) 1568
[5] A. Lisowska-Oleksiak, Int. J. Electrochem. Sci. 11 (2016) 1997 - 2017
