Conformal coating of TiO2 shell on silicon nanoparticles for improved electrochemical performance in Li-ion battery applications

A scalable wet chemical process for conformal TiO2 coating on silicon nanoparticles is investigated for Li-ion battery applications. The stable core-shell composite nanoparticles along with polyacrylic acid (PAA) binder was studied as an anode in Li-ion batteries and compared with bare-Si as a control. By limiting the charge capacity to 1500 mAh g (1), we established stable cycling (zero fade) for over 50 cycles for the coreshell compared to inferior stability (only 30% capacity retention) of the bare-Si nanoparticles at 0.1C rate. Stable capacity of 800 mAh g (1) at 1C rate over 100 cycles was also demonstrated for the core-shell nanoparticle electrode. Transmission electron microscopy and X-ray photoelectron spectroscopy characterizations indicate that in absence of TiO2 the solid electrolyte interface (SEI) layer which forms around Si was about 8-10 nm and composed of Li2O and LiF. In contrast, the SEI layer around the TiO2 shell has been thinner (about 2-3 nm) and composed of LiF and LixPFyOz, that stabilized the surface leading to improved cycling stability. Thinner SEI layer and its composition led to lower charge transfer resistance while the interface between the composite and the Cu-current collector has better adhesion compared to the bare-Si electrode. Impedance spectroscopy measurements confirmed the above. (C) 2017 Elsevier Ltd. All rights reserved.