Why and How Poly(acrylic Acid) Stabilizes and Structures Si/C Supraparticles for Li‐Ion Batteries: Unraveling PAA–Si/C Interactions From Dispersion to Electrode Integration

In lithium‐ion battery silicon anodes, achieving reliable electrode processing, consistent electrochemical performance, and mechanically stable electrodes remains a challenge. One strategy to overcome these limitations is to assemble silicon–carbon (Si/C) nanoparticles with alloy‐like Si–C bonding into micrometer‐sized secondary particles (“supraparticles”) by spray drying. Without additives, the supraparticles are irregular and fragile; therefore, a polymeric binder is introduced to enable their controlled formation. This study establishes a foundational methodological framework to investigate the interactions of poly (acrylic acid) (PAA) with Si/C during supraparticle formation. In aqueous dispersion, PAA adsorbs onto the Si/C surface via weak hydrogen bonding. Subsequent ionization of carboxyl groups generates electrostatic repulsion between particles, stabilizing the dispersion. Upon spray drying, PAA forms a flexible, hydrogen‐bonded polymer network that crosslinks particles without covalent attachment to silanols. Drying electrodes at 120°C preserves this network, enabling volume‐change accommodation and high‐capacity retention (1996 mAh g −1 at the 100th cycle). In contrast, drying at 200°C generates PAA anhydrides and ester linkages with Si–OH groups, which reduce compliance, leading to lower Coulombic efficiency and faster fading (1353 mAh g −1 at the 100th cycle). These findings highlight binder chemistry as a key lever in designing durable Si/C electrodes.