With an extremely high theoretical energy density, solid-state lithium-sulfur (Li-S) batteries (SSLSBs) are emerging as one of the most feasible chemistries; however, their energy efficiency and long-term cyclability are severely hampered by the lithium metal (Li) dendrite formation during repeated discharge/charge cycles and the shuttling of aggressive polysulfide intermediates between two electrodes. Herein, we report (difluoromethanesulfonyl)(trifluoromethanesulfonyl) imide anion [N (SO 2 CF 2 H)(SO 2 CF 3)]−, hereafter DFTFSI−, as a designer anion for high-performance polymer-based SSLSBs. In contrast to the widely used bis (trifluoromethanesulfonyl) imide anion [N (SO 2 CF 3) 2]−(TFSI−), DFTFSI-based SSLSBs provide superior interfacial stability against Li, extremely high discharge and areal capacities, very high Coulombic efficiency, and long-term cyclability, surpassing the reported literature values, in terms of gravimetric energy density. This work opens a new door for accelerating the practical deployment of SSLSBs in the future.