Delicately Designed Cyano-Siloxane as Multifunctional Additive Enabling High Voltage LiNi_(0.9)Co_(0.05)Mn_(0.05)O_2/Graphite Full Cell with Long Cycle Life at 50 ℃

摘要

Lithium-ion batteries (LIBs) adopting layered oxide cathodes with high nickelcontent (Ni ≥ 0.9) always suffer from extremely poor cycle life, especially atelevated temperatures and higher charging cut-off voltages. Adding smallamounts of functional additives is considered to be one of the most economicand efficacious strategies to resolve this issue. Herein, cyano-groups areintroduced innovatively into a siloxane to delicately synthesize a novelcyano-siloxane additive, namely2,2,7,7-tetramethyl-3,6-dioxa-2,7-disilaoctane-4,4,5,5-tetracarbonitrile(TDSTCN). Encouragingly, 0.5 wt. TDSTCN additive enables ultrahigh nickelLiNi_(0.9)Co_(0.05)Mn_(0.05)O_2/graphite (NCM90/Gr) full cells with dramaticallyincreased cycle life, especially at an elevated temperature of 50 ℃ and a highcharging cut-off voltage of 4.5 V. The characterizations reveal that theTDSTCN additive can scavenge HF and promote the formation of robuststable interface layers on NCM90 cathode and Gr anode due to the synergisticeffects of cyano-groups and Si?O bonds. These results reveal the greatsignificance of designing one single additive with several functional groups inenhancing the comprehensive electrochemical performances of high Ni LIBs.