A Dual-Functional Conductive Framework Embedded with TiN-VN Heterostructures for Highly Efficient Polysulfide and Lithium Regulation toward Stable Li-S Full Batteries.

Lithium-sulfur (Li-S) batteries are strongly considered as next-generation energy storage systems because of their high energy density. However, the shuttling of lithium polysulfides (LiPS), sluggish reaction kinetics, and uncontrollable Li-dendrite growth severely degrade the electrochemical performance of Li-S batteries. Herein, a dual-functional flexible free-standing carbon nanofiber conductive framework in situ embedded with TiN-VN heterostructures (TiN-VN@CNFs) as an advanced host simultaneously for both the sulfur cathode (S/TiN-VN@CNFs) and the lithium anode (Li/TiN-VN@CNFs) is designed. As cathode host, the TiN-VN@CNFs can offer synergistic function of physical confinement, chemical anchoring, and superb electrocatalysis of LiPS redox reactions. Meanwhile, the well-designed host with excellent lithiophilic feature can realize homogeneous lithium deposition for suppressing dendrite growth. Combined with these merits, the full battery (denoted as S/TiN-VN@CNFs || Li/TiN-VN@CNFs) exhibits remarkable electrochemical properties including high reversible capacity of 1110 mAh g-1 after 100 cycles at 0.2 C and ultralong cycle life over 600 cycles at 2 C. Even with a high sulfur loading of 5.6 mg cm-2 , the full cell can achieve a high areal capacity of 5.5 mAh cm-2 at 0.1 C. This work paves a new design from theoretical and experimental aspects for fabricating high-energy-density flexible Li-S full batteries.