High-Performance Carboxymethyl Cellulose Integrating Polydopamine Binder for Silicon Microparticle Anodes in Lithium-Ion Batteries

Silicon microparticles (SiMPs) have been gradually explored as the anode materials for lithium-ion batteries (LIBs) because they have higher tap density and lower cost than nano-structured Si and thus are more suitable for commercial high-energy battery applications. Developing a binder to alleviate the volume effect of SiMPs and ensure electrode stability during cycling is an effective method. Here, we propose a water-soluble binder by integrating carboxymethyl cellulose (CMC) with polydopamine (PDA) prepared from an alkaline aqueous solution, and the conventional buffer tris, an organic substance, is discarded to avoid problems during electrode preparation. The obtained binder CMC-10% PDA exhibits higher viscosity and better mechanical properties than CMC due to the strong interaction between CMC and PDA through hydrogen bonds and some covalent bonds. The SiMP anodes with the binder (the Si@ CMC-10% PDA electrodes) demonstrate excellent cycling stability (above 1700 mAh g-1 at 0.2 C after 1000 cycles) and rate performance (1269 mAh g-1 at 4 C) and can deliver a high area capacity above 3 mAh cm-2 at a Si load of 1.36 mg cm-2. The full cells composed of the Si@CMC-10% PDA anodes and lithium iron phosphate (LFP) cathodes can maintain an 80% capacity retention after 50 cycles, demonstrating practical application potential.