Although several principles have been recognized to fabricate a nominal "better" binder, there continues to be a lack of a rational design and synthesis approach that would meet the robust criteria required for silicon (Si) anodes. Herein, we report a synthetic polymer binder, i.e., catechol-functionalized chitosan cross-linked by glutaraldehyde (CS-CG+GA), that serves dual functionalities: (a) wetness-resistant adhesion capability via catechol grafting and (b) mechanical robustness via in situ formation of a three-dimensional (3D) network. A SiNP-based anode with a designed functional polymer network (CS-CG10%+6%GA) exhibits a capacity retention of 91.5% after 100 cycles (2144 ± 14 mAh/g). Properties that are traditionally considered to be advantageous, including stronger adhesion strength and higher mechanical robustness, do not always improve the binder performance. A clear relationship between these properties and ultimate electrochemical performance is established by assessing the rheological behavior, mechanical property, adhesion force, peel stress, morphology evolution, and semiquantitative evaluation. This study provides a clear path for the rational design of high-performance functional polymer binders for not only Si-based electrodes but also other types of alloy and conversion-based electrodes.

Shape-persistent, conductive ionogels where both mechanical strength and ionic conductivity are enhanced are developed using multiphase materials composed of cellulose nanocrystals and hyperbranched polymeric ionic liquids (PILs) as a mechanically strong supporting network matrix for ionic liquids with an interrupted ion-conducting pathway. The integration of needlelike nanocrystals and PIL promotes the formation of multiple hydrogen bonding and electrostatic ionic interaction capacitance, resulting in the formation of interconnected networks capable of confining a high amount of ionic liquid (≈95 wt%) without losing its self-sustained shape. The resulting nanoporous and robust ionogels possess outstanding mechanical strength with a high compressive elastic modulus (≈5.6 MPa), comparable to that of tough, rubbery materials. Surprisingly, these rigid materials preserve the high ionic conductivity of original ionic liquids (≈7.8 mS cm −1 ), which are distributed within and supported by the nanocrystal network-like rigid frame. On the one hand, such stable materials possess superior ionic conductivities in comparison to traditional solid electrolytes; on the other hand, the high compression resistance and shapepersistence allow for easy handling in comparison to traditional fluidic electrolytes. The synergistic enhancement in ion transport and solid-like mechanical properties afforded by these ionogel materials make them intriguing candidates for sustainable electrodeless energy storage and harvesting matrices.

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