Stable cycling of practical high-voltage LiCoO2 pouch cell via electrolyte modification
Chao Tang, Yawei Chen, Zhengfeng Zhang, Wenqiang Li, Junhua Jian, Yulin Jie, Fanyang Huang, Yehu Han, Wanxia Li, Fuping Ai, Ruiguo Cao, Pengfei Yan, Yuhao Lu, Shuhong Jiao
Abstract
Nitriles as efficient electrolyte additives are widely used in high-voltage lithium-ion batteries. However, their working mechanisms are still mysterious, especially in practical high-voltage LiCoO 2 pouch lithium-ion batteries. Herein, we adopt a tridentate ligand-containing 1,3,6-hexanetricarbonitrile (HTCN) as an effective electrolyte additive to shed light on the mechanism of stabilizing high-voltage LiCoO 2 cathode (4.5 V) through nitriles. The LiCoO 2 /graphite pouch cells with the HTCN additive electrolyte possess superior cycling performance, 90% retention of the initial capacity after 800 cycles at 25 °C, and 72% retention after 500 cycles at 45 °C, which is feasible for practical application. Such an excellent cycling performance can be attributed to the stable interface: The HTCN molecules with strong electron-donating ability participate in the construction of cathode-electrolyte interphase (CEI) through coordinating with Co ions, which suppresses the decomposition of electrolyte and improves the structural stability of LiCoO 2 during cycling. In summary, the work recognizes a coordinating-based interphase-forming mechanism as an effective strategy to optimize the performance of high voltage LiCoO 2 cathode with appropriate electrolyte additives for practical pouch batteries.