Synthesis and Characterization of TiO2@SnO2 Nanocomposite as Viable Anode for Lithium-Ion Batteries

With the market growth and increasing development of hybrid electric vehicles (HEVs) and electric vehicles (EVs), high-energy density and high-power materials are needed. SnO2 is one of the proposed materials to replace the industry standard graphite (372 mAh g-1), thanks to its high theoretical capacity of 1411 mAh g-1,1; but its use is hindered by low cycling stability due to the volume expansion/contraction during alloying/dealloying reaction respectively. In this regard, a composite anode material based on SnO2 and anatase TiO2 have been prepared using commercial SnO2 nanopowder and Ti-isopropoxide as starting materials. A sol-gel step, consisting in controlled hydrolysis of Ti-[O-iPr]4 in SnO2 dispersion followed by thermal annealing in inert atmosphere, yielded the composite made of SnO2:TiO2 in the approximate ratio 3:1. Structural characterization was pursued by XRD, SEM, TGA and Raman spectroscopy. Electrodes have been prepared using high-molecular weight PAA as binder, which is a greener alternative than PVdF and has better mechanical stability towards tin volume changes upon lithiation. Cyclic voltammetries at different scan rates revealed a linear relationship between the peak current and the square root of scan rates, with an estimated lithium diffusion coefficient in accordance with literature2,3. Prolonged galvanostatic cycling shows improved stability and average specific capacity of 908 mAh g-1 at 1000 mA g-1, together with remarkable rate capability. PEIS applied every 10 cycles revealed a stable SEI upon cycling. Two main factors concur in determining this behaviour, namely: (i) the efficient dispersion of SnO2 and TiO2, which act as volume buffering matrix; (ii) the formation of a stabilized SEI by VC additive in the electrolyte.