Aqueous Comb-like Polymer Binder for the Silicon/Carbon Anode with Improved Interfacial Stabilization and Lithium Transport

An aqueous comb-like random copolymer (PBBSEA) is designed for silicon/carbon (Si/C) anodes, synergistically achieving interfacial stabilization and rapid lithium-ion transport. Such ester and phosphonate groups, as well as alkyl side chains of PBBSEA, enable deformable noncovalent bonds and rigid covalent bonds with oxygen-containing groups over Si/C particles and graphite surfaces, thus leading to decreased slurry viscosity and more uniform electrodes. Concurrently, the phosphonate groups easily coordinate with the copper current collector, substantially suppressing the detachment of active materials with the improved electrode peel strength. The low glass transition temperature of PBBSEA endows exceptional elasticity, thereby effectively accommodating silicon volume expansions and maintaining the electrode’s structural integrity. Furthermore, the favorable binding energy between PBBSEA and Li + is expected to regulate local solvation structure and then promote lithium-ion migration from electrolytes to electrodes. Particularly, a stable solid electrolyte interphase (SEI) rich in inorganic components is fostered to form so as to enhance the interfacial ionic conductivity and stability. In terms of these advantages, the introduction of PBBSEA enables the Si/C anode to deliver a capacity retention of 67.4% after 200 cycles at 2 C, surpassing the pristine carboxymethyl cellulose electrode (60.4%). Meanwhile, the NCM811||Si/C full cell employing the PBBSEA binder exhibits diminished polarization, superior voltage retention (95.5%), as well as improved electrochemical performance. These results provide insight into the molecular strategy of the aqueous polymer binder, which is expected to extend the practical applications of the Si/C anode with saved industrial costs and improved safety.