Heavy-Duty Performance from Silicon Anodes Using Poly(BIAN)/Poly(acrylic acid)-Based Self-Healing Composite Binder in Lithium-Ion Secondary Batteries

Abstract

Natural abundance and high theoretical capacity make silicon a promising anode material in Li-ion batteries (LIBs). However, repeated cycling causes the pulverization of Si particles due to the large volume expansion that results in their rapid breakdown, delamination from the current collector, loss of electrical contact, and thick solid–electrolyte interphase (SEI) formation. This results in their poor performance. To overcome these drawbacks, the application of functional polymers as binders to silicon anodes has emerged as a competitive strategy. In this regard, here, the design, synthesis, and application of a highly robust n-type self-healing polymer composite poly(bisiminoacenaphthenequinone)/poly(acrylic acid) (P-BIAN/PAA) as a binder for Si anodes is reported. On its application, P-BIAN/PAA was evaluated to (i) provide mechanical robustness to the large volume expansion of Si particles, (ii) maintain electrical conductivity within the electrode laminate, and (iii) facilitate the formation of a thin SEI by restricting the extent of electrolyte decomposition on the surface of anode because of its low-lying lowest unoccupied molecular orbital (LUMO) that empowers its n-doping in the reducing environment. As a result, Si anodes could be stabilized for over 600 cycles of charge–discharge with a high reversible capacity of about 2100 mAh g–1Si, ∼95% capacity retention, and >99% Coulombic efficiency. The extent of suppression of electrolyte decomposition that led to a facile and thin interphase-SEI and the corresponding interfacial components with respective impedance values were not only theoretically evaluated but also supported by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and dynamic-EIS. Further, the postmortem characterization of the anode by X-ray photoelectron spectroscopy (XPS) justified the thin SEI formation on Si anode with P-BIAN/PAA composite binder.