Construction of dual crosslinked network binder via sequential ionic crosslinking for high-performance silicon anodes

Nowadays, silicon has become a promising anode active material for lithium-ion batteries due to its high specific capacity. However, traditional binder materials cannot effectively restrain the volume expansion of silicon during lithiation/delithiation. Inspired by the growth process of climbing plants, we sequentially crosslink sodium alginate with calcium ions and hyperbranched polyethyleneimine to construct a dual crosslinked network binder. During the sequentially crosslinking, sodium alginate preferentially crosslinks with Ca 2+ to form the “trellis” network, which restricts the free movement of hyperbranched polyethyleneimine and guides it, like “vine”, to gradually anchor on the surrounding “trellis” through hydrogen and ionic bonding. In this dual crosslinked network, the ionically crosslinked sodium alginate maintains the anode structural integrity; the anchored hyperbranched polyethyleneimine forms strong multidimensional hydrogen bonds with silicon nanoparticles through its amino-rich branch chains; and the network utilizes the bonding reversibility of hydrogen and ionic bonds to repeatedly eliminate the mechanical stress and self-heal the structure damages caused by the volume change of silicon. Benefited from the multifunction of the dual crosslinked network, the silicon anode has achieved an excellent electrochemical performance with a specific capacity of 2403 mAh·g −1 at the current density of 500 mA·g −1 after 100 cycles. Graphical abstract