Self-Healing Ion-Conductive Binder for High-Performance SiO_x Anodes in Lithium-Ion Batteries

Abstract

Volume expansion during repeated cycling is the primary cause of degradation of SiO_x anodes, impeding their practical application in next-generation high-energy-density lithium-ion batteries. Herein, a self-healing polymer binder incorporating both dynamic covalent and hydrogen bonding interactions is developed to accommodate volume changes and enhance the stability of SiO_x anodes. This self-healing binder (PPC) is prepared through the physical cross-linking of poly(α-lipoic acid) (PLA) and poly(acrylic acid) (PAA), together with the ion-conducting choline chloride (ChCl), which induces the formation of a network structure. Physical cross-linking effectively dissipates the stress and strain induced by the SiO_x expansion. And in this self-healing network, rigid PAA provides structural integrity, whereas elastic PTA with dynamic S-S bonds serves as a buffer, enabling a tunable balance between mechanical strength and flexibility to accommodate lithiation-induced volume expansion. As expected, the SiO_x electrode with the PPC binder demonstrates a decent performance with a specific discharge capacity of 998.6 mAh g^-1 after 200 cycles at 2000 mA g^-1, corresponding to a capacity retention of 85%. Meanwhile, the binder enabled the SiO_x||NCM622 full cell to achieve remarkable capacity retention of 95.1% after 100 cycles at 0.5 C.