High-performance polymer binders for silicon-based anodes: Advances in molecular design and applications

Silicon-based anodes represent a pivotal innovation for circumventing the energy density limitations inherent in current lithium-ion batteries (LIBs), chiefly because of silicon's exceptional theoretical specific capacity (4200 mAh/g). Nevertheless, its significant volume expansion (approximately 300 %) during electrochemical cycling presents critical challenges, such as electrode pulverization, continuous rupture and reformation of the solid electrolyte interphase (SEI), and rapid capacity fading, which collectively hinder commercial viability. Contemporary research paradigms to mitigate these issues primarily revolve around intrinsic material modifications-such as nano-structuring, carbon coating, alloying, and polymer binder composites-each yielding considerable advancement. Notably, while nano-structuring and alloying approaches aim to ameliorate volume strain from a crystallographic and mechanical perspective, carbon coating and polymer binder strategies primarily function through extrinsic confinement mechanisms, concurrently enhancing electrical percolation. Among these, polymer binders, albeit used in minimal quantities, fulfill an indispensable role. This review delineates the landscape of mainstream binder categories and their molecular tailoring strategies, presenting a balanced appraisal of their respective merits and drawbacks. It methodically encapsulates advanced tactics including graft modification, crosslinking, and copolymerization, deciphering their operational principles and molecular interaction mechanisms through sophisticated structural design. Moreover, it proves the profound impact of molecular engineering on the electrochemical behavior of silicon-based anodes, thereby furnishing both theoretical underpinnings and pragmatic directives for the advancement of binder technologies.