A core-shell composite sulfur particle containing a core of elemental sulfur having homogeneously dispersed particles of a conductive carbon and a polyelectrolyte polymer; and a shell containing a hybrid membrane coating of branched polyethyleneimine (bPEI) on the core and at least one sequential set of a negatively charged clay nanosheet and a further coating of bPEI encapsulating the core is provided. In the sulfur particle the dispersed particles of conductive carbon are associated with the polyelectrolyte polymer. A cathode having an active material containing the core-shell composite sulfur particle and a sulfur loading of 1.0 mg S/cm2 to 10 mg/cm2 and a battery containing the cathode are also provided.