Esterification Modification for Interfacial Affinity Enhancement of Biogum Binders With Silicon/Carbon Anodes

Biogum binder can effectively suppress the volume expansion of silicon (Si) anodes through strong interactions via hydrogen bonds with oxygen-containing functional groups, but its application on Si/carbon (Si/C) anodes still faces severe challenges of poor interfacial compatibility and insufficient interfacial adhesion. Herein, an esterification modification strategy is proposed to shift the interfacial affinity of the biogum binder from Si to carbon, thereby improving compatibility with the carbon component of Si/C anodes. Through dehydration reactions induced by heating under mixing, hydroxyl groups in tara gum (TG) react with carboxyl groups in propanoic acid (PPA) via esterification to prepare TG-PPA binder, which effectively reduces the content of hydrophilic hydroxyl groups. TG-PPA can disperse uniformly on Si/C anodes to effectively relieve the internal stress caused by volume expansion and maintain the electrode structure stability. Meanwhile, TG-PPA can form a uniform coating layer on Si/C anodes to suppress interfacial side reactions and form a uniform and compact SEI layer. As a result, Si/C anode with TG-PPA displays an initial Coulomb efficiency up to 72% and delivers a capacity of 550 mAh g^-1 after 100 cycles. Esterification modification overcomes biogum bottlenecks in Si/C anodes and enables high-value use of renewable polymers for high-performance binders.