Synthesis of Polyanionic Cellulose Modified Waterborne Polyurethane and Its Application in Lithium‐ion Batteries

ABSTRACT Waterborne polyurethane (WPU) is an environmentally friendly polymeric material characterized by its flexibility, tunable mechanical properties, chemical stability, and green aqueous system. These attributes endow it with substantial application potential in silicon anodes for lithium‐ion batteries, effectively addressing challenges such as electrode pulverization, detachment of active materials from current collectors, and repeated rupture/reformation of the solid electrolyte interphase (SEI) caused by volume expansion of silicon anodes. In this study, a novel WPU@PAC composite binder was constructed by blending WPU with polyanionic cellulose (PAC). This design utilizes the elasticity of WPU and the rigidity of PAC to synergistically enhance mechanical properties and interface adhesion through interactions such as hydrogen bonds, effectively suppressing the volume changes of silicon particles and maintaining the integrity of the electrode. Experimental results show that the silicon anode with the optimized WPU@PAC2 as the binder exhibits excellent electrochemical performance: the initial discharge specific capacity reaches 1117 mAh/g, the capacity retention rate after 100 cycles is as high as 88.61%, and it also has good rate performance. This composite binder provides an effective solution for addressing the bottleneck of silicon anodes and developing long‐life lithium‐ion batteries.