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Despite great interest in a Li–S battery, soluble polysulfides as charge/discharge intermediates pose an important challenge to realize commercial Li–S batteries. For building physical barriers to reduce a diffusional loss of those species, chemical surface-trap-sites have been proposed, but experimental evidence about the trapping interaction hasn't been reported. Here, highly crosslinked polymer-electrolyte coating layers with electron-donating groups were designed to bind lithium polysulfides. An ester group with a high spatial density was shown to be a strong candidate to bind lithium polysulfides. Spectroscopic evidence for the presence of lithium bonds between the lithium polysulfides and the electron-donating groups is reported for the first time. An electrochemical charge/discharge model is also proposed, which can explain the electrochemical behavior within the insulating polymer layer.