The industrialization of all-vanadium flow batteries（VFB） is currently hindered by the inherent trade-off between proton conductivity and vanadium ion rejection in ion exchange membrane materials.To address this challenge,a novel membrane architecture was innovatively proposed by constructing a composite membrane loaded with S-SN nanosheets.The performance of the composite membrane was systematically evaluated through micro-morphology characterization,physicochemical analyses including proton conduction and mechanical strength,as well as battery polarization behavior and constant-current discharge stability tests.The results demonstrate that the prepared composite membrane achieves a coulombic efficiency of 96.4% and an energy efficiency of 76.81% at a high current density of 200 mA/cm².After 500 cycles,the membrane exhibits excellent cycling stability with a capacity retention of 74.91%.By precisely regulating the membrane structure, this innovative design successfully resolves the balance dilemma of ion-selective transport,providing a new strategy for developing cost-effective and stable energy storage membranes.