Ambidextrous Polymeric Binder for Silicon Anodes in Lithium-Ion Batteries

摘要

A new type of polyamide imidazole(PAID)polymer with two functional groups for tight binding with silicon(Si)particles and carbon black is investigated as a binder for the Si anode in lithium-ion batteries(LIBs).PAID is synthesized via three reaction phases.The first phase is polyamide polymerization(p-PAID),the second phase is formation of imide and imidazole rings(i-PAID),and the last phase is ring cyclization for the PAID structure.Among these stages,i-PAID shows ambidextrous binding characteristics for LIBs.The planar π-conjugated backbone in the i-PAID provides a strong π-π stacking interaction with carbon black,thus sustaining the electrical conduction pathway in the Si electrode during cycling.The amine and carboxylic acid functional group in the f-PAID have a strong interaction with Si particles,which efficiently suppresses the volume expansion of the Si electrode,confirmed by in situ electrochemical dilatometry and ex situ SEM observation.The Si anode with the bifunctional/-PAID binder shows not only a higher reversible capacity but also a greatly enhanced cycle performance over 200 cycles in comparison to the Si anode with a simple polyimide binder.This ambidextrous polymer binder offers a new opportunity to positively impact the development of a mechanically robust Si anode for lithium-ion batteries.