Fabrication and performance of electrochemically grafted thiophene silicon nanoparticle anodes for Li-ion batteries

In this work, we developed thiophene-grafted Si nanoparticle anodes for Li-ion batteries. The surface of Si nanoparticles was chemically modified with thiophene molecules via an electrochemical grafting process. This study is an overture for future endeavours where the thiophene layer on the modified Si- nanoparticles will function as an anchor point when co-polymerised with conducting polymers to produce a chemically bonded Si/conducting polymer anode composite. This in principle should mitigate the loss of electrical connection with Si due to any structural breakdown that may occur during cell cycling. Furthermore, the effect of the thiophene layer on the capacity and the cyclability of the Si electrode was apparent where the new material retained ~39% of the starting capacity after 60 cycles, compared to the unmodified Si electrodes, that merely lasted for 10 cycles with only 4% capacity retention. This is due to the thiophene layers which create an artificial solid electrolyte interphase around the Si nanoparticles protecting them from degradation. Additionally, the viability of using conducting polymers as anode composites under charging/discharging conditions was investigated via electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) to conclude whether or not n-doping of the conducting polymer is required in such applications.