A mechanoresponsive elastomeric binder toughened using a supramolecular zwitterionic network for silicon microparticle anodes†

Silicon microparticle (SiMP) anodes are promising candidates for lithium-ion and post-lithium-ion batteries owing to their fewer interfacial reactions and higher tap density than nanostructured silicon anodes. However, the intractable volume expansion/contraction of micro-sized silicon upon cycling results in severe particle pulverization/disintegration and an unstable solid-electrolyte interphase. Binders play an essential role in dissipating huge mechanical stress and promoting the lithium-ion diffusion kinetics of silicon anodes. Herein, we design a mechanoresponsive dual cross-linking elastomeric network that incorporates a supramolecular zwitterionic reorganizable network into a hydrogen-bonded polyacrylic acid network to stabilize the interphase and improve cycling stability of silicon microparticle anodes. Such dual-network design enables effective stress dissipation and spontaneous crack repair via sequential dissociation of weak supramolecular zwitterionic interaction and strong dimeric H-bonds of zwitterions upon repeated lithiation/delithiation. Benefiting from these merits, the resultant SiMP anodes using the mechanoresponsive elastomeric binder exhibit a high reversible capacity of 1625.1 mA h g⁻¹ at 2.0 A g⁻¹ after 400 cycles. The assembled full cells with LiNi_0.8Mn_0.1Co_0.1O₂ cathodes afford a reversible capacity of 105.2 mA h g⁻¹ after 100 cycles. This work demonstrates the great potential of mechanoresponsive elastomeric binders in developing state-of-the-art high-performance silicon microparticle anodes toward high-energy-density lithium-battery applications.