Hybrid polymer network cathode-enabled soluble-polysulfide-free lithium–sulfur batteries

Among the emerging ‘beyond lithium-ion’ technologies for maximized sustainability, lithium–sulfur (Li–S) is a favoured chemistry because of its exceptional energy density from the conversion of sulfur, an element in abundant supply. However, the dissolution of several intermediate polysulfides formed during conversion leads to rapid performance degradation over cycling. Here we address this issue by sulfurizing a hybrid polymer network with polyphosphazene and carbon as a cathode for Li–S batteries. With rich sites to re-bond and adsorb dissociative sulfur species, this hybrid polymer network circumvents the formation of soluble polysulfides and enables a unique, reversible inserting conversion reaction. Thus, our cathode delivers both high capacity (~900 mAh g−1cathode) and excellent cycling stability in Li–S coin cells, with a pouch cell demonstration of projected energy density of ~300 Wh kg−1 and 84.9% capacity retention after 150 cycles. The strategy can be extended to other cost-effective, recyclable polymers, advancing sulfur-based batteries towards practical energy storage application.