<p>Lithium–sulfur (Li–S) batteries with high energy density are promising for next-generation energy storage but suffer from poor cycle life due to instability of the lithium anode. Commercial graphite anodes used in lithium-ion batteries could be viable for replacement of lithium metal as anode in Li–S batteries. However, graphite anodes are incompatible with the commonly used ether-based electrolytes in Li–S batteries due to the Li⁺ ion and solvent co-intercalation into graphite interlayers, which leads to exfoliation. Here, we report the stabilisation of graphite anode by <i>in-situ</i> formation of quasi-solid-state electrolyte (QSSE) in Li–S batteries. The QSSE is formed by the ring-opening of molecular ethers induced by metallic molybdenum disulfide sulfur cathode host to produce long-chain polymers. The resulting gel polymer matrix exhibits ionic conductivity (1.51 mS cm⁻¹) comparable to that of liquid electrolyte and provides sufficient redox chemistry for the sulfur cathode without co-intercalation into the graphite anode. Li–S pouch cells based on <i>in-situ</i> formed QSSE and graphite anode show a specific capacity of ~ 1200 mAh g⁻¹ and 90.3% capacity retention after 200 cycles. Our design addresses the electrolyte limitation associated with graphite anode, enabling graphite to be used in ether-based solvents for safe, cost-effective and stable Li–S batteries.</p> Graphical abstract <p></p>