Electrically conductive shell-protective layer capping on silicon surface as anode material for high performance Lithium-ion batteries.

Abstract

Rational design and construction of effective silicon (Si) electrode structures to relieve large volumetric changes that occur during the charge/discharge process remain as significant challenges for the development of robust lithium-ion batteries. Herein, we propose an electrically conductive poly[3-(potassium-4-butanoate) thiophene] (PPBT) capping layer on Si surface (Si@PPBT) to serve as the active material and be used in conjunction with a common polymer binder as an approach to tackle issues emanating from volumetric changes. The PPBT protective shell layer provides the system with tolerance towards variations in active material volume during cycling, improves the dispersion of Si nanoparticles in the binder, enhances the electrolyte uptake rate and provides a strong adhesion force between the Si/ carbon additives/ current collector, thereby helping to maintain electrode integrity during the charge/discharge process. The π-conjugated polythiophene backbone structure also allows the Si core to maintain electrical contact with carbon additives and/or polymer binder, enabling the formation of effective electrical transport bridges and stabilizing solid electrolyte interphase (SEI) layer growth. The integrated Si@PPBT/ CMC anode exhibited high initial coulombic efficiency (84.9%), enhanced rate capability performance, and long cycling stability with a reversible capacity of 1793 mAh g-1 after 200 cycles, 3.4 times higher than that of pristine Si anodes with same CMC binder (528 mAh g-1). The results suggest that the Si@PPBT design presents a promising approach to promote the practical use of Si anodes in lithium-ion batteries, which could be extended to other anode materials exhibiting large volume changes during lithiation/delithiation.