Spidroin-Inspired Hierarchical Structure Binder Achieves Highly Integrated Silicon-Based Electrodes

As a promising component for next-generation high energy lithium-ion batteries, silicon based electrode has attracted increasing attention by virtue of ultrahigh theoretical specific capacities. Nevertheless, fast capacity fade posed by tremendous volume changes during the lithiation and delithiation process remains a huge challenge before large-scale applications. Inspired by spidroin, we herein develop a tenacious hierarchical structure binder for tolerating huge volume change of silicon-based anode, which is prepared through simply mixing aqueous poly(acrylic acid) solution, and oily N-methyl pyrrolidone solution containing a tetrazole groups based copolymer (PPB) of polyacrylonitrile and poly(ethylene glycol) bisazide. Such an aqueous-oil binary solution based blend (AOB) binder exhibits a spidroin-like hierarchical structure. In the AOB binder, hydrophobic PPB polymer condensates in the mixture solution to form crystalline region within submicron-sized irregular spherical domains as the rigid node of the molecular chain segment similar to β-sheet of spidroin; while water-souble, amorphous poly(acrylic acid) mimicks the α-helix structure of spidroin, and builds up a network structure by linking with PPB via ionic bonding similar to the interactions between repetitive amino acid sequence segment in the primary structure of spidroin. Benefited by these, AOB binder enables both high tensile strength and elasticity, and superior adhesion of electrodes, therefore apparently stabilizing silicon-based anode structure and rendering prolonged electrode cycle life. This work marks a milestone in developing state-of-the-art silicon-based electrodes towards high energy density lithium battery applications.