Understanding the effect of p-, n-type dopants and vinyl carbonate electrolyte additive on electrochemical performance of Si thin film anodes for lithium-ion battery

Abstract

Amorphous silicon (Si) is one of the most prospective high performance anode material for lithium-ion batteries and thin films of this material are promising for microbattery applications. Undoped, p- and n-type doped Si thin films were deposited by madgnetron sputtering on a three-dimensional current collector designed to accommodate the volume expansion of anode upon charge-discharge cycling, improve the active material adhesion, and to enhance the rate capability of the anode. The designed Si thin film anodes with and without doping were first investigated in lithium cell using various electrochemical techniques confirming the positive effect of doping on their performance. Raman spectroscopy was performed before and after cycling the electrodes to further elucidate such effects. The trends in change of an electrolyte during first lithiation/delithiation were observed by in situ Raman technique. Along with this, the morphology features of a solid electrolyte interphase (SEI) layer formed on the surface of the electrode and its modifications upon addition of 5% vinyl carbonate (VC) to the electrolyte were studied. The n-type doping and unique SEI layer formed with poly(VC) polymeric species suppressed the electrode crack formation preventing the capacity loss due to the material disintegration upon cycling, which resulted in an outstanding cycling performance of Si thin film with the capacity of 1305 mAh g−1 retained over 400 cycles.