Ambidextrous Polymeric Binder for Silicon Anodes in\nLithium-Ion Batteries

Abstract

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