A lithium–sulfur (Li–S) battery based on multielectron chemical reactions is considered as a next-generation energy-storage device because of its ultrahigh energy density. However, practical application of a Li–S battery is limited by the large volume changes, insufficient ion conductivity, and undesired shuttle effect of its sulfur cathode. To address these issues, an aqueous supramolecular binder with multifunctions is developed by cross-linking sericin protein (SP) and phytic acid (PA). The combination of SP and PA allows one to control the volume change of the sulfur cathode, benefit soluble polysulfides absorbing, and facilitate transportation of Li⁺. Attributed to the above merits, a Li–S battery with the SP–PA binder exhibits a remarkable cycle performance improvement of 200% and 120% after 100 cycles at 0.2 C compared with Li–S batteries with PVDF and SP binders. In particular, the SP–PA binder in the electrode displays admirable flame-retardant performance due to formation of an isolating layer and the release of radicals.