Reducing SF6 (as gas cathode) in Li batteries is a promising concept for the double benefit of mildly converting greenhouse SF6 and providing a high theoretical energy density of 3922 Wh kg-1 . However, the reduction process is hampered by its sluggish kinetics. Here, cobalt phthalocyanine (CoPc) molecules immobilized on porous carbon matrix are, for the first time, introduced to the LiSF6 chemistry to deliver an enhanced energy density. It is revealed that the high redox potential of Co(II)Pc/[Co(I)Pc]- (≈2.85 V) facilitates the formation of Co(I)N4 sites to catalyze the SF6 electrochemical reduction. By using highly porous holey nitrogen-doped carbon nanocages as carbon matrix, the LiSF6 cells deliver a high discharge voltage of 2.82 V at 50 mA gC+CoPc -1 and an unprecedented areal capacity of 25 mAh cm-2 at 0.1 mA cm-2 , much superior to previous results. This work opens up new possibilities for high-efficiency conversion of SF6 in lithium batteries.
Keywords: Li SF 6 batteries; cobalt phthalocyanine; porous carbon; reduction kinetics; sulfur hexafluoride.
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