PEO coupling with NiO/C3N4 heterojunction facilitates lithium salts dissociation and polysulfides conversion for all-solid-state lithium-sulfur battery

All-solid-state PEO-based Lithium–sulfur (Li-S) battery has very attractive development prospects, since it is hopeful to avoid the safety problems caused by liquid electrolyte and make it possible to apply lithium metal anode. Unfortunately, PEO used in Li-S battery is faced with the problems of low ionic conductivity and shuttle effect. Herein, a kind of NiO/C3N4 heterojunction was synthesized and doped into PEO-based polymer electrolyte(P-NiO/CN). There exist built-in electric fields at the NiO/C3N4 heterojunction interface. Li+ cation and TFSI− anion of lithium salts can be dissociated rapidly under the electric field force to produce more free lithium ions. Hence, the highest ionic conductivity reaches 1.2 × 10−4 S cm−1 at 30°C. It is also observed that the heterojunction enhances the interface compatibility between polymer electrolyte and lithium anode, which results from the promotion of the formation of Li3N in SEI layer. Besides, NiO and C3N4 can effectively adsorb polysulfides to alleviate the shuttle effect. As a result, the Li | P-NiO/CN | S cells exhibits an initial capacity of 810 mAh g−1 and remained 411 mAh g−1 after 250 cycles.