Coil-to-Stretch Transition of Binder Chains Enabled by "Nano-Combs" to Facilitate Highly Stable SiOx Anode

The commercialized binder carboxymethyl cellulose sodium (CMC-Na) is considered unsuitable for micro-sized SiOx anode as it cannot endure the large volume change to retain the conductive network during repeated charge/discharge cycles. Herein, a small amount of silicon nanoparticles (SiNPs) is added during slurry preparation process as "nano-combs" to unfold the convoluted CMC-Na polymer chains so that they undergo a coil-to-stretch transition by interaction between polar groups (e.g., -OH, -COONa) of polymer and SiNPs' large surface. Through maximizing the utilization of binders, a uniform conductive network is constructed with increased interfacial contact with micro-sized SiOx. As a result, the SiOx electrode with optimized (10 wt%) SiNPs addition shows significantly improved initial capacity and cycling performance. Through revisiting CMC-Na, a currently deemed unqualified binder in SiOx anode, this work gives a brand-new perspective on the failing mechanism of Si-based anode materials and an improving strategy for electrode preparation.