Self-Formation CoO Nanodots Catalyst in Co(TFSI) 2 -Modified Electrolyte for High Efficient Li-O 2 Batteries.

The major challenges for Li-O 2 batteries are sluggish reaction kinetics and large overpotentials due to the cathode passivation resulting from insulative and insoluble Li 2 O 2 . Here, a novel nanodot (ND)-modified electrolyte is designed by employing cobalt bis(trifluoromethylsulfonyl)imide (Co(TFSI) 2 ) as an electrolyte additive. The Co(TFSI) 2 additive can react with discharge intermediate LiO 2 and product Li 2 O 2 to form CoO NDs. The generated CoO NDs are well dispersed in electrolyte, which integrates both the high catalytic activity of solid catalyst and the good wettability of soluble catalyst. Under the catalytis of CoO NDs, Li 2 O 2 is produced and deposits on the cathode together with them. At the recharge process, these well dispersed CoO NDs help to decompose solid Li 2 O 2 at a lower overpotential. The Li-O 2 cells with Co(TFSI) 2 exhibit a long cycle life of 200 cycles at a current density of 200 mA g -1 under a cutoff capacity of 1000 mAh g -1 , as well as a superior reversibility associated with the Li 2 O 2 formation and decomposition. The study is expected to broaden the range of electrolyte additives and provide a new view to developing highly dispersed NDs-based catalysts for Li-O 2 batteries.