Soft-hard segment elastic binder with extended hydrogen-bond networks enables ultrafast Li+ transport and long-life cycling in silicon anodes

Designing advanced polymer binders offers an effective route to mitigate the severe volume expansion of high-energy-density micron silicon (SiMP) anodes for practical applications. However, most existing binder studies prioritize mechanical robustness while overlooking ionic conductivity, which is equally critical for electrochemical performance. Here, we report a multifunctional polymer binder formed by a synthesized polyurethane-based polymer, polyphenol polyurethane (PUTA) and polyacrylic acid (PAA), aiming to achieve a synergistic balance between high ionic conductivity and mechanical integrity. PUTA integrates poly tetramethylene ether glycol (PTMEG) soft segments for simultaneous Li + transport facilitation and elastic stress relief, while tannic acid (TA) is introduced to serve as a branched, rigid anchoring center within the hard segment to provide abundant phenolic hydroxyl groups for forming a dynamically reversible, physically cross-linked hydrogen-bonded network upon blending with PAA, simultaneously ensuring structural robustness, uniform stress distribution, and self-healing of microcracks during cycling. As a result, the Si anodes enable over 90% capacity retention across a broad current density spectrum, from 0.5C to 4C. The augmented PTMEG segment, which leads to superior Li + diffusion in dynamics tests surging to 9.44 × 10 −10  cm 2  s −1 , has certified its ability of Li + transportation. Moreover, the full battery with LFP loading at 13.05 mg cm −2 as cathode and SiC1800 as anode also boasts impressive long-term cycling stability.